I'll have to echo what Pinotnoir said...

Basically my Q6600 (which I build 2 years ago) runs wow just fine.
If your budget is very limited you might go this way too.

However, if you're building a new system today, it makes a lot more sense to go with a newer and more powerful system.
The core i7 processors go onto a newer motherboard, which supports more ram and that ram is more powerful too. Neither of these will go onto a Q6600 board.
Even the lowest end i7 processor leaves room for upgrading to a more powerful version down the road; even if you never upgrade it, its a lot more powerful then even an overclocked Q6600.
Any i7 will likely play the next warcraft expansion (or other game) as a boxer, not sure if a Q6600 (and slower ram etc...) can say the same.

The i7 costs less now then the Q6600 did when it had been out a similar amount of time.