Comp can't power radeon?

I never would have come to this conclusion at first, but after experimentation.... I have a radeon 9500 softmodded to 9700 in an albatron PX845PEV Pro. Here's the weird part... all is well when the radeon is at stock speed 275/540, the 3.3v drops to almost 3v, but everything works. The more I OC the radeon the lower the 3.3 gets, all the way down to 2.9 when the radeon is at 390/580. Now it is my theory that this voltage drop causes 1 of 2 things to happen... 1.- If Fixed AGP/PCI is selected in the bios the comp instantly freezes in any 3d game 2.- Fixed AGP/PCI is disabled then the computer is able to play the 3d game, but the sound drops out and stutters and exiting the game causes a complete system freeze. Sounds like I need a new psu?? I'm not so sure... I've tried 4 different ones. I started with an enermax 365, then I tried 2 different models of enermax 465s and now I'm using an antec true power 430w. My question to the guys well experienced in power issues is could the mobo simply not have the power for the overclocked radeon? (I thought the radeon power adapter was supposed to solve that) Do you think a bigger psu may fix this...say maybe a true power 550w? Thanks.

BTW the 3.3v rail isn't constantly that low, that is the "Low" recorded by mbm while Im running a 3d game. Thanks.