Let's move you here for some better results.
If you have the hopes of Crossfire in the future, then the X1900XTX might be your best choice. RIght now there isn't an SLI-capable motherboard available that supports Conroe, but the Conroe-ready 975X boards do support crossfire. Be warned, the X1900XTX is a very warm card and consumes a lot more energy than the 7900gt/gtx. It's also a noisier card. ATI has somewhat resolved this with the X1950XTX, but that card was just launched and might not be available when you are ready to buy.
Give what you cannot keep to gain what you cannot lose.