yes get dual channel memory, it will work better for gaming
you could look into getting a pentium 4 with hyperthreading, better for gaming. <http://www.newegg.com/app/Viewproduc...rchFor=pentium
If u want to spend a little more money, get a 64 bit, alot better for gamers.
Asus is definently the mobo to get though.
You shouldn't really need to worry about the power supply, unless you get a bigger HD, very fast processor (64 bit or 3.0GHz or bigger).
Make sure u have enough cooling in ur case, if it is running nice and cool, it has less tendency to glitch than if it were running very hot. Try to keep it from 42-48C