HTPC/Gaming GPU

After upgrading from my dell dimension (celeron cpu) to my current system I've been indecisive about what to do with it. It was originally planned for gaming then I suddenly decided I wasn't that bothered and was going to use it as a HTPC in an unnecessarily large case. I'm back to looking at getting a gaming system setup but would like to keep a quiet PC when in normal use. Any suggestions for a decent GPU that is less than ~£120, that could be xfired/sli'd in future, and is realistically possible to use multiple monitors with, (Eyefinity or equivilant) whilst still being quiet

Second hand 560/560ti or ideally 6870 probably. Chose one with a decent cooler for the quietness.

which one would be better? I've heard conflicting things. Does it depend on the game (ie will some games prefer ATI some Nvidia)

Depends on the game, depends how many monitors you have. In general the 560ti is the fastest of the three I mention, but the 6870 is the only one that'd work with three monitors.