I switched to a sata III board, and didn't notice much difference. The new board loads windows in maybe 5 seconds less than the sata II board. The older board actually had faster boot speed overall due to the bios settings. You won't find a sata III board with any core2 duo cpus, so keep what you have and wait for a cpu/board/ram upgrade.
Thanks for your response. I'll take your advice and just get the SSD SATA 3 to go with my SATA 2 board.