I too suggest getting a X1900XTX. It will be better in teh long run.
The biggest argument I ever hear about paying extra to get a XTX is that you can simply OC the XT to XTX speeds. While this is true, it still isn't a good selling point to simply save a few bucks on a XT, because yuo can also OC the XTX to even higher speeds than the XT.
I can't help you on the PSU, I have trouble with them myself.