actually lack of L3 cache isn't going to hurt gaming too much, Tom's had an article about this a ways back when the first athlon II's came out and there wasn't much of a difference
While this is true of the duals and even the tri core, the quad still takes a fair hit by the lack of L3. bit-tech done a fantastic article showing why the cheap quads aren't the bargin they're made out to be too. While GPU is more likely to be the limiting factor in most systems the quad still isn't a compelling purchase especially priced so close to the intel. I still stand by the i3 tho since intel is likely to change socket again so hopefully a cheap 750 can be picked up at a later date. Again while phenom hex cores match the i7 920 at stock in heavily multi threaded apps, the i5 and i7's oc like dreams.
TBH for gaming I would go for the Athlon 440 and overclock it. Its very close to the phenom II 720 in performance. Unless your upgrading an AM2+ or AM3 system anything above the phenom II 550/Athlon quads price steps into intel territory especially if your confident overclocking. Since the 440 is so close to the 720 I would tend to avoid the athlon quads or phenom duals. Its different however if you intend to run at stock, and by all means go for the quad.
taken from tom's on benchmarks http://www.tomshardware.com/reviews/athlon-ii-x3,2452-10.html