Yikes ...

Err, just so you know, on most modern motherboards, I'm pretty sure the ram is capable of running asynchronously with the system bus.

Which means that you can have a 400 mhz fsb and 333 mhz ram, or vice versa.

In fact, my slightly aged P4 has an effective 800mhz fsb (quad-pumped 200mhz) and ddr-400 ram, but my roommate's even older p4 has a an effective 533fsb and still uses ddr-400. Further, the AMD64 lines have 1ghz fsb speeds, and ALSO use DDR400.

Even further back, my old thunderbird's board was capable of running it at 133fsb, or 100fsb, and capable of independently adding up to 33 mhz to the system bus speed to drive ram (so with a 133-fsb athlon, you could run the memory at 166mhz, if you could find the modules to drive that high).

In other words, these things don't have to match. It's nice when they do (makes access and scheduling a little easier), but they don't have to. You should be more concerned with what your motherboard supports ... but in general DDR-400 is backwards-compatible with earlier generations -- effectively, it's just higher quality versions of slower memory, rated for higher clock speeds.

I'd more recommend looking up your motherboard on crucial.com's memory selector, and seeing what it's compatible with. Go from there.