The only downside of going with faster memory than you need is that the higher the speed rating, the slower the timings will likely be. Cheap PC3200 memory is not going to perform as fast as cheap PC2100 memory when running at 266MHz.
When I say timings, I'm talking about those latency numbers you often see in the specs. For example, you might see 2-5-5-7 on an average stick of PC3200 DDR. But on an average PC2100 DDR stick, you would likely see faster timings (lower numbers) in each position. The lower the better.
Now many might argue that you're only talking about a 1-2% margin of performance here. That's true. But to be technically correct, it really offers you no advantage and can actually hurt performance (even if only by a small percent) to get the PC3200 stick.
Besides, your next major upgrade will likely require DDR2 or some other future form of memory. Therefore, hoping that you can use it in your next system isn't a likely outcome...
~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Albert Einstein
[tab][navy]For general rules and guidelines to get better answers, click here:[/navy] faq219-2884