Oh and I might just disclose my setup :

2x 7950's (a lucky pair, found an awful lot of blocks considering they're the lowest hash rate)
4x 7970's (my solid grunts, do a lot of the lifting in the pools)
2x 7990's (beautiful cards, just a shame their price sky rocketed otherwise I'll be running loads of these babies!)
4x 290's (the latest addition to the setup giving 780kh/s out of the box with no config tweaks, I'm very impressed)

Cheers,
FlyingW