Cache cards speed up the 68k quite a bit, I wonder why Apple didn't make use of cache on all their towers.

Why do people push the PPC so much? The only reason I have PPC PDS cards is because I need a weird combination of 5 Nubus slots and a PPC chip for some hardware. Turning a 68K into a PPC is not the best bang for the buck, especially when people just want their 68K to be faster (and cache WILL speed things up quite a bit).