Ugh.... No. You don't have to run your fsb and memory synchronously if you don't want. I have a 2700+ w/ a 333 MHz FSB and I can run my memory (3200 Corsair CAS2) at 3200(400 MHz) or 2700(333 MHz). You have to make sure your mobo supports whatever settings you choose.
<font color=red>The solution may be obvious, but I can't see it for the smoke coming off my processor.</font color=red>