i will recommend the 6970 crossfire,
i also recommend that hyper 212 as well, dual fans
using i7 950 @ 4 Ghz, ASUS Rampage III Forumla :), Mushkin 6 GB 1600
its doing very well so far. very fast. only a couple of minor glitches in bad company 2 is all i've seen.
I hope it runs Duke...