I never had to reinstall the OS to uninstall AMD drivers on 4890/6950 or 7970. I don't know what you were doing. As of the last 12 months at least, uninstalling AMD drivers is very easy.
Just go to C:\AMD\Support --> Click on the AMD Driver folder --> Setup --> Next --> Uninstall. Follow all the steps, restart the computer. Download the new driver from AMD.com, install, restart the computer. Done.
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VitaX, among those choices and that resolution, HD7970 Vapor-X is the cheapest, the fastest and will scale the most with overclocking. It would get my vote hands down. However, depending on what games the OP plays, if they are not too GPU demanding, one can get a $280 HD7950, overclock that and then next year, if more performance is necessary, sell that card and upgrade to something faster, or even stretch it to 20nm in 2014. Really for modern games I would imagine at that resolution you'd want 2x 7950/7970/670/680 cards. But if the choice is among those 3 cards, the Vapor-X 7970 Ghz. Personally I would hesitate to spend $400+ on any of the current generation cards simply because Tahiti has been out on the market for 12 months now. I don't really like the idea of spending $400+ on a 1 year old GPU as it's going to end up with a similar case as buying a $400+ GTX580 near the end of its life. The cooler on the Vapor-X and the 7970 Dual-X are fairly comparable in terms of their heat dissipation. If I had to buy a 7970 now, I'd just get the
$360 1Ghz Sapphire Dual-X. I just don't see how the Vapor-X is worth $60+ more.