There are quite a few for sale on computer forums. Its worth signing up to a few sites you can pick up some bargains on there, its definately not always a good idea to buy new especially with computer parts.
The Q6600 seem to have actually gone up in price to ~£150 new now with the pound getting weaker, but second hand they can be had all day long under £120 depending on how good they clock. I've been offered a good clocking G0 Q6600 with a Freezer Pro cooler for £115 delivered, but I don't actually need it have managed to find a Q9450 instead for cheap