I've gotten haggled SO much for buying this card in various forums, but why wouldn't you want the best of the best? I've got a couple of people looking at my card on Ebay, but no one ever commits until the last minute or so of the auction, so I don't know. There are two 7950GTX's on Ebay as we speak for around $415 shipped.
I did have a single pipe 7900GS, but I fried it. When I bought the new one (didn't want to deal with Dell's bullshit), it was a dual-pipe. There's a tiny piece of the case, right next to where the heat sinks are, that you'll have to remove. I just got a pair of pliers and broke the piece out. Not hard to do at all.
If I sell my old 7900, the swap will end up costing me $225.
At this point I'd like to offer a disclaimer. To some people, $400 is a bunch of money, to some others it isn't. I'm not saying this card is the end-all be-all or that it will solve all of your graphical problems. With MY PARTICULAR set up I noticed way above average gains in game. I don't want people cursing my name in the forums because they thought they'd be able to run Oblivion at 100 frames per second on full graphics settings. If you want that, go buy a desktop.