I'd say the 6800GS is the best call. It can play med-high and if you had to you could OC it. Since it'll only be till the end of the year at most you should be more than fine with it.
go eVGA WHATEVER you buy and then use the step-up program to buy the G80 when it comes out. I have no idea how many times i've said this. GO eVGA!!! they'll take you old card and you just pay the difference! no gimmick. 100% trade in for price paid on invoice. Why would you bother with anything else...