if you want an accelerator it would be best to get a 1200 which is really designed for expansion as it has a trapdoor option.
Perhaps you don't even need one as it is over twice the speed of the 600.
You can get the ACA 630 for the 600, however I was reading that many 600s need to have the CPU reflowed to work correctly with the ACA. Seems that the original C= soldering process was not very good.
