It looks like the dedicated hardware plugin boxes (UAD etc) use traditional DSP chips like the Analog Devices SHARC for their horsepower. Is anybody using graphics card processors via GPGPU (General Purpose GPU) approaches such as CUDA or OpenCL to accelerate plugins?
Updated: I discovered the Acustica Audio Nebula plugins which can use CUDA. Looks like much of the net chatter about these plugins is about excessive latency, possibly attributable to CUDA, and the fact that using CUDA doesn't actually increase the overall max track or plugin count.