I have an Elrod Silver PC on a MKII and have tried a few others - they all provided an upgrade from stock, IMO. I agree 100% with antigrunge2 - isolation seemed to yield great benefit as well. I tried Isoacoustic and Stillpoints and actually ended up using Cardas Myrtle Wood blocks as I preferred them the best.
The Phoenix was the largest upgrade I have made and highly recommend it.
Happy listening!