For me the biggest decision would be my CPU. I am pretty much the opposite of toyota, I believe GPU >>>>> CPU for gaming. But with that said, I've had the same motherboard since the Radeon 2900XT days and the same CPU since I got a 4870. Now I am using this combo with my 5870. If I got a 68xx, would my CPU still be up to task? I imagine it has to start limiting me sooner or later. A new card I can swing, a new mobo/DDR3/CPU/card, the wife won't go for. :/
It seems like AMD's GPU division is pulling ahead of the CPU division by a good amount.
Anyway, these are the dilemmas that new video cards bring.