That psu should run a 9800gt, when I first got my 9800gt I had it running on my 400w psu w/o a prob, until i got my bigger one of course, but that 500w one should be able to handle it no prob. Now for the case and mobo part, whenever I build a pc I always make sure the case supports micro atx or atx just cause of the fact that I will know it will work. I most people say it should fit, but id rather know for sure and not have to worry about it..
- Justin