333 Vs 400

How much difference does it make to 3DMARK if you run the same system at 200 X 12 and at 166 X 14.5 ?

I know that programs like SETI benefit a lot from higher FSB speeds. I use my PC for a lot of things but playing games is the only really intensive thing I do?

Basically, EVERYTHING benefits from a wider pipe, which is effectively what a higher FSB is.

I know my 3dmark scores went up when I went from a 133mhz FSB to 180 - the end result was only a 140mhz overclock roughly (1.66ghz to 1.8 ghz), but the memory bandwidth increased dramatically.

I would imagine 200 vs 166 would yield similar results - not so dramatic, but an increase nonetheless.

If you can do the 12x200, run a suite of benchmarks (and also do some gaming to get a real world feel for it) and then compare it to the 14.5x166.

I think you'll choose the former.