This is potentially true, but it's not a slam dunk because CPUs may be much more powerful than whatever you can build into a disk controller cost-effectively.  This may not be true (a high-performance ASIC implementation may be tiny; this is not unheard of in the world of bit-banging algorithms), but it is worth considering.  I'll have to look into what compression algorithm they used, and whether you can get away with something smaller/less power-hungry than a Core 2 on a disk controller.