RM300 budget for mobo.... you should go for BIOSTAR TForce 6100-AM2 instead of the MSI. Low end MSI is often problematic and a lot of incompatibility with many hardwares.

TForce 6100-AM2 is stable, caps are great (solid capacitors around the CPU)... and most important, the board is using blue pcb instead of ugly red.

512x2 better. Any of those two will do (if you're thinking of value RAM).

6100 has on-board graphics, 550 doesn't. but that's not very important

6100 have 2 IDE connectors, 550 only have 1 IDE.

most important is 6100 is priced below RM300 ... 550 is above RM300.

bigger cache gives significant advantage if you do video encoding.

i've compared a sempron 256k L2 with an athlon64 512k L2 .... both are from the same core revision, and both are overclocked to the same speed at 2.7ghz. athlon64 is faster.

From my observation, I haven't seen any X2 3600+ that can overclock as well as an X2 3800+. Probably EE processors don't overclock well nowadays.