1 Gig of memory is plenty even for gaming. Unless you're a graphic designer (and why would you be using windows if you were?!) you don't need more than a gig of RAM. I have a gig and I can alt + tab out of any computer game with no less than 300Mb free of RAM. I play doom 3, desert combat and FarCry, all of whihc are high-demand games, so it's everything you need.
The dual channel lark doesn't really do much, I did exactly what you did. I had 512 and slapped in an extra 512 (remember to get RAM with exactly the same latency, etc). The only noticable difference was the alt + tabbing out of huge applications. The dual channel apparently helps only for on-board sound and some other minor stuff like that.
You could always get an extra 512 or gig in the future if you *really* need to...