Need some help choosing

Ok, like many I'm building a new machine but have some problems. I'm a gamer, but not hardcore(I dont need to run doom3 at 300FPS in 2048x1536 AAx8)

Right now I'm running a P4-2.4, 512MB RDRAM (yes I know, horrible) BFG 6800GT AGP.

Problem 1)

So initially I was looking to buy a new MOBO that still supports the soon to be antique AGP. Would it be better to:

A) Sell the 6800GT and upgrade to PCI-E so that I can buy a future-ready MOBO?

B) Buy an AGP MOBO, hope it lasts a year or two, then upgrade?

Problem 2)

CPU - AMD for sure
a) dual core? <--- leaning this way, possibly 3800+
b) non-dual?

Problem 3)

a) Dual channel DDR?
b) DDR2?

Any opinions would be helpful, thanks.

Dual core is not for gaming. Games only use one core, the other one creates problems at this point. While you can expect patches to keep dual cores from crashing in game, it will be 3 years or more before there will be games that make up the clock speed difference.