Honestly, I just bought a q6600 and built a system around it. The prices on current processors is pretty good, and I don't see Nahalem being "cheep" any time soon (nor do I like being the extreme early adopter!). I'd much rather build a $1000 rig every year than build a $2000 rig every 2 years.
As far as current tech stands, I doubt an e8500 or q6600 (or one of the newer 45nm quads) is going to have any problem running any game/program for a while. What are you doing with your machine (gaming, encoding, etc?). Honestly, if it's just a standard gaming/media/etc... machine, I would just drop a new $200 chip in it right now (of after the next price drop if you can wait). If you don't need Nahalem right away (and really... there aren't many of us here that can say we "need" it), wait for a bit for some good boards to come out, ddr3 to come down, etc... and then build (you'll get better prices and better value).
Then again, it's even cheaper to just overclock the hell out of your chip. Get yourself a sunbeam core contact freezer for $35 (after a $5 MIR) from the egg and go to town.