3200 mixed with 2700?

I just wanted to know if say I got a stick of 512 DDR pc3200
Seeing as right now I have 2 sticks of 256 pc 2700 samsung. Will these memorys conflict?
Because I want to get one stick of 512
Then another later on so i can phase out these samsung chips.
Or is there not really much of a difference in 3200 vs 2700 an just stick with 2700?

Also is it for certain that rate ram would work with my Epox 8rda+?
I'm also planning on getting a mobile barton 2500+

My current rig is
Amd 1700+ @ 1.8
Epox 8rda+
ThermalRight Sk-7 hs
ati radeon 9500 pro
512 samsung 2700 ddr
80 gig maxtor
etc

They will work together, but their settings will be limited by the 2700.

As long as you can run the FSB at 200 mhz then you can run the pc3200 ram at rating if you don't have the old pc2700 in there. The pc2700 is only rated for an fsb of 166, so that will slow you down.