If you can afford it, I would step up to the 850. It overclocks better than the 700, and has the same 2.9ns NEC cache as the 700. With a GFD and the KA7-100, I wouldn't be surprised if you hit 1.1ghz...
Also, I have heard that Abit is working on a adapter to use Socket "A" T-birds and Durons with Slot "A" mobo's. The next generation of the T-bird and the Duron will have the new "Mustang" core early next year, so when that adapter comes out, you should be able to use your KA7-100 with them. By then, any early compatibility issues should be resolved... Have Fun!