if you're buying a gaming rig then don't shell out the extra cash for the dual-core. it doesn't help, unless you're going to be ripping divx files or something in the background. dual-core doesn't mean "twice as fast", it just means that it can go just as fast in two apps/games at once.
also, of all the games around at the moment only BF2 needs anything near to 2gb ram, and that's only because they do absolutely shitty things technology-wise.
the trick with cpus (and to some extent, also graphics cards) is to do your own home work. checkout the benchmarks and review sites and compare performance vs $$$, and i'm sure that you'll find that the current pricepoint is sitting at around the Athlon 64 3200/3400. i don't know exactly how it is in the US, but for example: the jump from 3000 Venice to 3200 non-venice 939 and from there to 3200 Venice over here are both about $35. then there's a $30 drop to the 3400 754, or $100 up to the 3500 939 (Venice). that $100 jump is the point where the price:performance ratio starts to taper off, and you have to look at it and decide how much you're willing to pay in order to have a few more frames per second.
