Intel Core i5 6500 - RM 899
MSI B150M Bazooka - RM 399
Kingston HyperX Fury 8GB DDR4 2133MHz RAM - RM 289
Palit GTX970 4GB GDDR5 Jetstream - RM 1399
WD Blue 1TB HDD - RM 225
Thermaltake Versa H25 - RM 139

Total: RM 3350 (Techview price inclusive of GST)

No need to change if it is still working and your PSU is totally fine to run this spec.

If you are worried about old PSU issue, you can think of changing to a better quality one like Seasonic PSU which can last for quite a long time. But for the time being, you can just reuse it and change it only if the new system is not working well with old PSU (like random reboot/shutdown/other kind of weird issues etc.).

The base frequency/speed of DDR4 RAM is 2133MHz, anything beyond 2133MHz is considered as overclocking and you will need a compatible mobo such as Z170 chipset mobo to take advantage of this feature. Faster speed will have faster operation speed but in real life usage, it is very hard to notice the difference unless you benchmark them. So just stick with 2133MHz if you aren't getting Z170 mobo because even if you get a super highly overclocked 3200MHz DDR4 RAM on H170/B150/H110 chipset mobo, you will only stuck at 2133MHz too due to chipset limitation.

RM 500 is impossible to build anything, the cheapest new CPU already costs RM 200 and no new CPU/mobo is using DDR2 RAM anymore so it is impossible unless you look for used item in Garage Sales.

But still budget is very low

If you are planning to adopt to latest technology and hardware, you need to abandon that DDR2 RAM and get DDR3/DDR4 RAM.

So minimum should be around RM 1.5K without monitor for entry level rig.

If you are a gamer and would like to play latest games at stable frame rate, I would suggest you to save at least RM 2K, the more the better of course.

Intel Core i3 4160 - RM 469
ASRock H81M-VG4 - RM 189
Adata 8GB DDR3 1600MHz Value RAM - RM 189
Sapphire R7 250 2GB GDDR5 - RM 349
WD Blue 1TB HDD - RM 219
FSP Hexa+ 400W - RM 129
Thermaltake Versa H25 - RM 149
BenQ GL2023A - RM 299

Total: RM 1992 (Viewnet price inclusive of GST)

Intel Core i5 6500 - RM 885
ASRock B150M-HDV - RM 399
GSKill NT 8GB DDR4 2133MHz Value RAM - RM 249
Palit GTX970 4GB GDDR5 Reference - RM 1399
WD Blue 1TB HDD - RM 219
FSP Hexa+ 550W - RM 199
Thermaltake Versa H25 - RM 169

Total: RM 3519 (Idealtech price inclusive of GST)

Intel Core i5 6500 - RM 885
Gigabyte H170N-WiFi - RM 589
GSKill NT 8GB DDR4 2133MHz Value RAM - RM 249
Palit GTX970 4GB GDDR5 Reference - RM 1399
Samsung 650 Series 120GB SSD - RM 219
WD Blue 1TB HDD - RM 219
FSP Hexa+ 550W - RM 199
Fractal Design Core 500 - RM 259
BenQ GL2460 - RM 539

Total: RM 4557 (Idealtech price inclusive of GST)

Ways to reduce cost:
1. Remove SSD.
2. Reuse your current SSD/HDD if you can.
3. Switch to cheaper case like CM Elite 130 (RM 199)

2.5K budget is quite hard to fit Skylake i5 + 24" monitor so I will use Haswell i5 instead.

Intel Core i5 4460 - RM 795
Asus H81M-K - RM 229
Kingston HyperX Fury 8GB DDR3 1600MHz RAM - RM 220
Leadtek GTX750 2GB GDDR5 OC - RM 485
WD Blue 1TB HDD - RM 225
FSP Hexa+ 550W - RM 189
Thermaltake Versa H25 - RM 139
BenQ GL2460 - RM 499

Total: RM 2781 (Techview price inclusive of GST)

To keep below 2.5K, either downgrade the i5 to i3 or change to smaller monitor.

It depends on your usage, your usage is light on CPU so i5 is enough, else you need to find another RM 500 for i7 but it won't bring significant benefit to you based on your usage.

GTX970 and R9 390 is having almost similar performance but GTX970 is having lower power consumption so you can pair it with mid range PSU, meanwhile R9 390 has an edge in those games which utilize more than 4GB VRAM but it is having higher power consumption which you need to get a decent 600W PSU to work with it, this will increase total cost needed.

Techview is selling Seasonic M12II EVO 620W at RM 399.

Or you can try Superflower Leadex 650W at RM 369.

Yes, they have but it is priced at RM 409 which is slightly over budget.

RM 299 still on but that's for non modular unit, Seasonic S12II 620W.

Is your normal usage include gaming?

2K for a rig with no hardware to reuse (including monitor) is impossible to fit an i5 and decent nvidia GPU FYI, you will end up with i3 + low/mid range GPU only due to weak RM + price hike + GST.

Intel Core i5 6500 - RM 885
ASRock B150M-HDV - RM 399
GSKill NT 8GB DDR4 2133MHz Value RAM - RM 249
Palit GTX960 2GB GDDR5 Reference OC - RM 899
WD Blue 1TB HDD - RM 219
FSP Hexa+ 550W - RM 199
Thermaltake Versa H25 - RM 169

Total: RM 3019 (Idealtech price inclusive of GST)

Intel Core i5 4460 - RM 795
Asus H81M-K - RM 229
Kingston HyperX 8GB DDR3 1600MHz RAM - RM 220
Gainward GTX750 1GB GDDR5 - RM 439
WD Blue 1TB HDD - RM 225
FSP Hexa+ 550W - RM 189

Total: RM 2097 (Techview price inclusive of GST)

Quite hard to squeeze in all the parts under 2K budget, if you can reuse your HDD (if you have one currently) then you can upgrade from 4th gen i5 to latest 6th gen i5.

Just trying to max out his available budget.

He posted 4k - 4.5k so why not

If your friend is getting an upgrade part-by-part path, I'll suggest to go for Intel platform, AMD socket is dead for current generation CPU, if you are getting LGA1150 socket, you still can upgrade to Haswell i3/i5/i7 later.

For max budget of RM 700, it is very hard to get those mentioned items to run Dota 2 at decent frame rate.

Intel Pentium G3250 - RM 229
ASRock H81M-VG4 - RM 209
Kingston 8GB DDR3 1600MHz Value RAM - RM 189
FSP Hexa+ 400W - RM 129

Total: RM 756 (Viewnet price inclusive of GST)

PSU might need to change next time when you upgrade the specs, unless you go for low power/low end GPU.

I need to know your exact GPU model to determine which PSU to buy.

According to their price list here, no more GTX960 for just RM 739. The cheapest starts with Zotac Single Fan version, RM 815 which is still quite affordable.