the best potential wise are the 7950's with 7970 PCB's which include:

Sapphire 7950 OC cards(950 mhz model black PCB)
MSI Twin Frozr 3 7950

and a foreign
Fire Hurrican A795

Sapphire Vapor-X gets special mention for cooling properties(as doing so is a gamble if you get a voltage locked or unlocked model for heavy overclocking purposes), though no 7970 pcb.