Well, if you like AMD is this not a bad route to go. Get yourself an AM3+ motherboard, like the Gigabyte 990FX UD3 for $150 and you can either crossfire or SLI down the road. Then when bulldozer eventually comes out, you can drop in an 8 core.
I don't know that you'll see a lot of difference between those two cards in games at 1080p. Mostly FPS bragging rights. So to me, it isn't worth it diminishing returns on your investment and so forth.