I want to say two things that you should take with a grain of salt, as I'm in no way an expert.
1) From a gaming perspective, I would advise you not to go for the 7950 GX2 right now. Considering that Directx10 is less than year away I'd say, right now you should get a budget graphics card right now (like the X1900XT you mentioned), and wait and see what comes out after Vista's release. I don't feel that getting a very expensive, top of the line graphics card is worth it, if it becomes obsolete six or eight months later.
2) I don't see the point of getting an LCD monitor, if you don't have any space problems. A good CRT monitor is still much more flexible in terms of resolutions, which is a great help for gaming from a long term perspective.
I hope I've helped.