Will my PC2100 hold me back?

Hi there, I'm about to upgrade to the soyo KT400 dragon ultra board and a 2600+ or 2700+ processor. I currently have 2 sticks of crucial 256MB DDR PC2100 ram, I'm wondering should I upgrade?

Will it hold me back a little or a lot, thanks.

I'm assuming if you go with the 2600 your getting the 333mHz version (166x2), in which case your memory would be holding you back unless you can overclock it to 166 so that the cpu and memory are in sync.