no, im not kidding, dual cores do not handle games as well as single cores, and the lower end X2s especially wont handle them as well.
Like an oced X2 4400+ would match if not fall short of the proformance of a 64 3700+. But with his graphics card he shouldn't be able to tell that big of a difference. And on the other side single's dont handle regular apps like dual cores do, im not saying that he should switch cpus i am just saying if hes only wanting this pc for gaming he should lean more toward either i higher end X2 or a single. but thats just my opinion.