I am having issues with my PC now, I think the culprit is my PSU so I need a replacement.

This is my system:
Videocard: Sapphire X1800XT 256MB
Processor: AMD Athlon 64 X2 4200+
Mainboard: Asus M2N-E AM2 nForce 570 Ultra
Memory: DDR2 800 2x512MB Corsair XMS2
Soundcard: Audigy 2 ZS & Sennheiser HD 212 DJ
PSU: COOLMAX 500W +12V1 18A
Soon I will be adding another 2GB of the same memory.

I am thinking about getting these two PSU, please tell me what you think of them or if I can get a better deal:
OCZ StealthXStream 600W
Thermaltake Purepower 500W

So your asking if you should replace a 500W with a different 500W?