Don't worry too much.
c2d will be outdated b4 u know it.
Intel officially announced its 45nm proccies today (they are already talking of 32nm, u believe that!!) Its all over extreme-tech
We shall have 45nm proccies in the markets in a year (6months according to intel).
And know what, I have a P4 1.5 GHz 256kb L2cache (the earliest ones

). So just buy a cheapo for the timebeing but a good motherboard. Upgrade sometime next year or the year after.