Help with upgrade

I recently bought a X800Pro\vivo@XTPE and it has made it obvious that I am now cpu limited. What do you guys think would be the best upgrade route keeping in mind I want to re-use as much of my current stuff as possible. My system specs:

XP2400+ @2325(15*155) Watercooled
A7N8X-X
1GB PC2700 Kingston HyperX
X800XTPE
Audigy2
400w Seasonic PS
80GB Western Digital HD
40GB Maxtor HD

I'm thinking A64 but which one, and Mobo, Ram? I would prefer not to have to replace my ram, but if I have too I will. I really don't want to spend more than around $400, but if it would make a big difference I could go as high as $500. What do you guys think?

Nice video card! Right now I would wait until the socket 939 CPUs are out and tested a little more....

Yeah, mobile Bartons would give you a little bit of a jump but a real upgrade that can be really 'felt' is going to be a complete move to Athlon 64.

You'll need a new mobo, PC3200 RAM, (Socket A heatsinks don't work with Athlon 64s for those who have them).

nForce4 mobos will be out soon and Socket 939 90nms have already been released, no sense going with Socket 754 at this time...

When is nforce4 supposed to be out? I don't want to wait to long, but I'm reasonable.