300 Watts is plenty for that system. You will have no problems with the power supply.
"In three words I can sum up everything I've learned in life: It goes on." -Robert Frost
May 17, 2001 4:55:48 PM
i use an enlight 400w with a similar system (athlon 900, etc). I decided to use something this powerful for a couple of major reasons: one, absolutely no worries about power, either now, or in the future. two, the fan on this baby is VERY powerful and quiet. so much so that the average temp on my athlon is 109 F. most people dont consider the power supply fan for cooling, but other than the HSF on the processor, it is the most important as heat rises. its a little more (*around 90.00), but a good investment.
I agree with Antivirus. Too much is better than too little.
Not all 300 watt PSUs are equal. GeforceFAQ.com recommends a PSU than can supply 20 amps on the +3.3 volt leg for the combination of an Athlon and a Geforce video card and not all 300 watt PSUs can do this. You may not need a 400 watt unit. The Enermax EG365P-VE, 350 watts, would do nicely. Costs only about $65, USD.
Anandtech has a good (if somewhat dated) article regarding power supplies. I suggest reading it for the general information but not necessarily for a recommendation.