I just got an antec true control 550
it seems pretty good even tho I wish atx power supplies had more current on the 3.3v and 5v rails
If you are serious about overclocking then you don't want yur psu to hold you back so i recommend atleast 500watt because you can get them at good prices these days
also i recommend for an athlon system that you atleast get 30a (or more) on the 3.3v and 5v rails, you prob won't even need 20a on the 12v rail
with my true control I have the 3.3v and 5v voltage adjustments turned all the way up and i barely hold the default voltage where as the 12v i can blast it all the up to like 12.47v
my antec 480 was not powerfull enough for me to hit speeds like 220 fsb because the rails would drop and my system would become unstable
but yeah i recommend getting atleast 500 with adjustable voltage pots like the antec 550 has