It depends on what 200w psu you're talking about. Some of the SFX supplies used in MATX systems are rated for AMD processors. Their 3.3v and 5v outputs are relatively strong, and the 12v is low.
Even these are intended for basic systems- HDD, Floppy, CDROM, processor fan and case fan- that's all.
Check the link above, if the psu is there then it definitely will work, just don't go for serious overclocking or a lot of peripherals.....