Have not heard these yet, thus unable to comment. Just check them out, and if possible audition/test them at a showroom and see which one suits your preference...

No exact cost yet as need to determine the source of the problem first. As with this speaker system, usually the most common source of problems is the potentiometer for volume control and stereo input socket for audio input. Usually will not be a 3 digit sum (under RM100) if the source of the problems are those that I've mentioned. The only time it will cost more, is if for example one of the power amplifier I.Cs failed/blown. Just PM me for detailed information.

Techno music? You may want to look at Altec Lansing range of speakers, such as Altec Lansing VS4621, for boomboxes. Otherwise you could also check out both Edifier M3400 or Edifier M3300SF... 

Im currently using using a pair of H4 with a H10, and trust me, this are DEFINITELY all rounders
They sound good for music, movies, games...hard to not like it, seriously. I would suggest you to go audition it at Cyntrix Tech shop at Puchong.

If you are on the lower end of the budget, then I would suggest Edifier Studio 7 (a.k.a Edifier R2700) or Edifier Studio 8 (a.k.a Edifier R2800) for active 2.0 speaker systems though both are pretty powerful at more than 100WRMS. Above that you may want to consider either HiVi Swans M50W, Edifier S530D or Edifier S730 (added Edifier as they are more widely available), which will be pretty loud also considering the small size of your room...

If below RM300 then that would be either Edifier M3300SF (best for music) or Edifier M3400. Above RM300 that would be Edifier HCS2330, and if can stretch to RM400+ then its Edifier C3. As for that Edifier C2X, can refer to this review: Special Interest -> Home Entertainment -> Audiophiles -> Edifier C2X review, (honest review/opinion) editied extras (PC Audio)...

What is the brand/model of your current speaker system? As for that cable, which one? Is it the right speaker cable, or the audio cable? For speaker repairs then can try me (just PM me if interested) though I'm located in KL area.

Given the genre of the music then I would suggest/recommend either Edifier Studio 7 (a.k.a Edifier R2700) or Edifier Studio 8 (a.k.a Edifier R2800) active 2.0 speaker system... 

You may want to look at the HiVi range such as the Swans M200 range. And alternatively you may want to consider an integrated amplifier with bookshelf speakers (pretty much mix and match)...

Looks like Logitech S-100. Methinks its time to replace these tiny speakers. Any 2.1 speaker system would sound a lot better than your current speakers... 

There's a high possibility of internal broken wire inside the plug and/or at the neck of the plug (where the cable joins the plug). Just cut it off and solder a new 3.5mm stereo plug.

Notice that front grill? Remove that first and you should find some screws holding down the driver and access to the internal hardware inside the casing...

For speaker systems with Bluetooth, you may also want to consider either Edifier PrismaBT or Edifier Spinnaker (our very own forum review here: Special Interest -> Home Entertainment -> Audiophiles -> Edifier E30 Review!, Took a while for me to write this up (PC Audio))...   

You may want to take a look at Edifier R1600T III as well, although its just 2.0 stereo speakers. According to specifications, this speaker has better low frequency (bass) response than Swans M10...

Try looking at Edifier M3400, Edifier M2300, or Edifier M3300SF (external review here: Overclock3D :: Review :: Edifier M3300SF 2.1 Speaker Set Review). As always, do audition/test the speakers first to see if it suits your listening preferences...

And what would be your budget range? 

You can want to try using the integrated audio first (usually most integrated audio solutions nowadays are pretty adequate). However if you have the budget to get a sound card like ASUS Xonar then go ahead and get it...

is speaker size on your concern? usually bose c5 is aim by user who does not have enough space to put speakers, plus money not issue.
u can have a lot of choices because the relation of "bigger size is better" is somewhat true...

lets say a pair of 5" bookshelf & int amplifier, like xls encore (from a forummer here named fx20) will cost you at the range of c5

i see... c5 or a5 both are OK-type speaker, my choice is a5 because "bigger = better" haha

a 5" like a5 can handle mid & midbass. it will be less unbalance tone and loss of detail being filtered out in crossover circuit. this is very obvious in near field listening.

c5 little satelite cannot, the space saving design rely the powerful subwoofer to help producing mid-bass. u will get the unbalance overtone and that's about it.

i never heard of "using bamboo" as a case material by traditional speaker maker

If primarily for music then at the lower end of the budget scale you may want to take a look at Edifier Studio 8 (a.k.a Edifier R2800, our local forum review here: Special Interest -> Home Entertainment -> Audiophiles -> Edifier R2800 Review (MASSIVE)(PICS), Reasonable priced Studio Speakers (Hi-Fi) ) for 2.0 system, or HiVi Swans M50W for 2.1 system. As for the higher end of the budget scale, there are too many choices and combinations to choose from. If spending more isn't a problem then you may want to look at ye olde Wharfdale DX-1 HCP which is quite musical in nature despite its position as a (compact) home theatre surround speaker system... 

That would be DA5000 Pro. Also S730D would be a good candidate as well. As always, try auditioning/testing those speakers to see which one suits your listening preferences...

Aye, the surround speakers should be at the back/rear (anywhere behind the table, can be as far as the wall) while the center speaker should be right at the center/middle of course...

Yes, you can connect your computer and/or music player to a micro/mini-Hifi system provided it has audio inputs (usually analogue and/or digital connection)... 

Could be the environment (if there are other speakers blasting then affects the overall sound), the music source/device (usually portable players and mobile phones have weak outputs), music quality (such as low bitrate MP3 file), and/or bad audio cables. Also perhaps you prefer "bright" speakers (have high trebles)...

z623 has crossover "hole" when u put the subwoofer in wrong location /phase, energy are wasted to another space. thats why u get the oohm beats without muddy bass.

u can walk around the listening area, sure got a spot suddenly all the bassy note kick back

r27/28 dont have separate sub unit, all sound get in ur face

Those Soundsticks can sound a little "thin", while the Aura is pretty much mono (no stereo separation). I would suggest auditioning/testing them and see which one you prefer...

Bassy? Perhaps the person in the showroom turned the bass dial up to almost full. Otherwise these speakers are very flat sounding (after all these are studio monitors thus considered HiFi quality). As for the Logitech Z623, (if not mistaken) the satellites are using phase plug for high frequency (treble) reproduction. That's a kind of "poor man's tweeter". Thus do not expect greats trebles from such speakers. In contrast, the Edifier R2700 and Edifier R2800 have real tweeters...

If you're a "bass head" then try looking at Logitech Z623 and perhaps Edifier Studio 7 (a.k.a Edifier R2700). As always, try auditioning/testing those speakers and see which one suits your listening preferences...