Buy all the other stuff (e.g., case, DVD-RW, etc.) before you buy a video card. I always buy the video card last since the prices continue to drop and newer models keep coming out. I also buy the CPU close to last for the same reason. I'm guessing you'll save $20-$30 if you wait 1-2 months to buy a 7800GT. Not a big savings, but it adds up
EDIT...or you could save ~$80 now and give up ~5% in performance (and SM 3.0) by buying a X850XT from the Egg for $204 shipped:
http://www.newegg.com/Product/Product.a...102505&CMP=BAC-dealmac&ATT=100106SR-RD
All depends on your preference and your willingness to wait. Keep in mind...the longer you wait, the more you "over-paid" for your existing parts (i.e., they tend to keep dropping in price right along with the video cards, though not as fast usually).