those old q6600s are BEASTS, lol. I know a guy who's still running one and doing fairly well at modern games with it, esp. if they are threaded. If you can do the bsel mod, you can get them running at 3ghz with very little danger, which is quite nice.
Oh absolutely. I haven't OC'd it, but stock with a HD5750 1GB the first game he had on it was the 2013 Tomb Raider, Played on Medium settings 40-50 FPS the whole time. And when the the day comes that the 5750 can't keep up anymore I'll slap a R9 270 in it and he will get another 3 years out of it. The main reason I got the q6600 aside from the price is I felt confident that even with it's age (2007 intro I think) I felt that it had a lot of life left in it. 7 Years ago dual-cores were mainstream and quad-cores were enthusiast. Now quad-cores are mainstream and 6-8 cores are considered upper edge, while dual cores are just now starting to fade out due to obsolescence. If that pattern holds true, by the time his Q6600 is too slow to play his games (will have probably OC'd to 3ghz by then...) he will be in high school (he's 11 now) and he will be getting a new gaming computer anyway.
I actually don't think the curve will remain stable over the next few years, but yeah, at $27, it's a good deal even if you have to upgrade tomorrow.
Sure thing, and he's had it since march and plays mostly light MMOs on steam. The whole build cost me $100 (its on my completed builds) and like you said, if it craps out tomorrow it was still worth it.