RAM, however, cannot overclock itself to accomodate higher FSB speeds.
Well...thats kind of untrue in my case. I have an AMD Athlon XP 2400+ FSB of 266 so of course by default in my BIOS I have it at 15x133 cause multi is locked and I don't care to OC this chip..not on this mobo.
Anyway...I have one stick of PC2700 ram and one stick of PC3200 ram...most people would think that both would be underclocked to meet the standards of PC2100 RAM, but this is not the case....my motherboard is set to BY SPD right now instead of me setting the frequencies to get the 1:1 ratio and it has my ram Overclocked (for the pc2700 anyway) to 2x199=398MHz, so just 2MHz short of the complete 400 PC3200 memory. My computer did that when it was just the PC2700 in there...decided to run it at almost PC3200 speeds and I've had no problems with it regarding instability or anything.
Generally though you want. You can have a slower CPU than the RAM...and have probably an easier time of your motherboard just OC'ing the ram to compensate like mine did......but if You have a fast CPU with 400FSB the RAM will definitely bottleneck it...unless it too can be overclocked to a perfect 2x200 for 400PC3200 ram.