^topic, im planning a build and im not sure either to go with 3GB of ram (ddr2 800) or if its better to go with 2GB (dd2 800) and run them in dual channel...

discuss.

dual channel

use the memory in pairs, SOOOO much faster

I would suggest using 2 identical RAM modules for dual channel (so not 3GB). Dual channel doubles memory bandwidth, and is supposed to increase performance, although I don't know how significant.

So yeah, 2x2GB or 2x1GB. Since RAM costs like nothing these days, I'd say 2x2GB.

Don't listen to those enthusiasts who would tell you to get 8GB of RAM or some bullshit like that, even 4 is probably more than you'd be able to use up.

Dual channel doesn't really increase performance that much.  Performance is still primarily based on latency, and dual channel doesn't really help in that regard.  Still, you'll get a speed boost, but probably not that much.
Do you need 3GB?  If not, I'd go 2GB.  But if you find that you're constantly running into swap space with 2GB, 3GB will give more performance than 2GB in dual channel.