quite a difference... but it would require a specialized mobo. IIRC SRAM is what is used in L1 and L2 cache, check the speeds that those can be run at with memtest86+, it's insane.
An added benefeit, IIRC, is that SRAM is not volatile - which means it does not lose the data contained when power is removed, which means you could simply (with a special driver/OS patch) power the system down and unplug it, then as soon as the HDD spins back up and inits itll be completely normal.