Your best bet is to just goto the Tom's Hardware Best Video Card for the money page... You'll find what you are looking for in price ranges. I would recommend getting a 1950XT. It still has gaming potential since it's not really that old, and also will do those resolutions for media center just fine. If you go on Newegg, you can probably get one for about $160 now.
Take that advice about the x1950xt, it's very good. The difference between GT and GTS is that the GTS is a bit better, but they're both bad value for the money IMO. If you want to play games they're both bad, if you want to watch HD movies a cheaper 8500GT is enough.
The x1950XT has a hair dryer fan, not what you want in a media center PC. The x1950PRO is also a good card, and isn't so loud.
I've got a 7900GS, and it is almost silent. At worst, you can buy an aftermarket cooler, like a Zalman vf700-Cu; one of those I have on a 7600GT is almost inaudible even on its high setting.