It depends why you want to speed up your A1200.
IMHO you would be better saving your money and buying something with a 68030 or higher - this is just a RAM/clock/co-processor unit. The RAM will mean your A1200 speed roughly doubles for some things anyway, and a co=processor will speed up programmes which are programmed to use it (e.g. Vista, raytracing apps etc) but things that have the 68020 as a bottle-neck won't speed up.
Getting something like a Blizzard 1230 will allow you to have a clock, RAM, co-processor AND a faster main processor. A 1230 Mk IV sped my A1200 up x9 (according to sysinfo).