For you to get both Morel Maximo and Tempo, you must have a pretty hefty budget. If so, I suggest you just stick with Tempo for the front, and ditch the rear. Then spend the extra $$$ on getting a good sub and amp. JL W3v3 or JL W0v2 together with a JL monoblock comes to mind.

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Added on February 17, 2012, 7:25 am

Instead of asking what can you do with RM4k, why not just tell what it is you find lacking from your current setup?

Personally I'd remove the rear speaker, sell it to get more money, upgrade the front components to a better one, get a new HU like a Clarion HXD2 (there are alot for sale 2nd hand), and if you still have the budget, get a better amp to power the front components and leave your sub and your Autocraft to power it. When you later have more budget change the sub and amp.

ok if you can live with a 2.0 bookshelf speaker, i think you dont even need to go for subwoofer upgrade.

maybe find more reputable ICE shops, like howiechoo from EA autoworks (bukit jalil) or KF audio (aman suria)

tell them what you need.
and from the looks of it, you only need a new HU, mid range component set and *POSSIBLY* an entry level amp replacement

your existing amp(s) and subwoofer, even if its "cap ayam" (well, sony isnt exactly cap ayam however in ICE, its kinda below reputable brands' entry level lol) i think can still be tuned to match with your new upgrades

and yes, your rm3-4k budget is a very healthy budget to fulfil that need, good luck

mid range or entry level is a "tiering" of products.
as the naming implies, a general complete setup for entry level is under 5k give/take
while mid range is above 5k to 10-20k, and anything beyond is basically high-end
and from the "tiers" out of a complete setup, each components will be respectively priced accordingly too.

or to make it simpler, visit a reputable component set ICE website, and select their component set speakers (2 or 3 way, suggest 2 considering your budget) that is priced in the middle level.
as a rough guideline, entry level components are between rm500-1.5k, while mid are around 1.5-3k+
anything less, my personal advice is to not even bother, especially when you're capable of forking out such budget, as it's just a waste of your time and money

entry level amps are between 1.5-2.5k+ btw. (yes these things tend to be a lot more expensive lol.)

price justification is a very subjective matter, however i believe to you, if its going to sound nice, it will be worth it, no?