Unfortunately, to future proof the board as much as possible, you'll need to spend a bit more than $200. I was thinking of the Gigabyte GA-965P-DQ6
for you, because it supports Conroe, but also supports Kentsfield (Intel's upcoming quad core CPU). With some luck though, the Gigabyte GA-965P-DS3
may support Kentsfield, although my guess is it will definitly need a BIOS update before being able to house a Kentsfield chip.