I use the Solid Tech Disc's of Silence under both my monoblocks. You could also use the Feet of Silence. I think they provide excellent isolation, and they are way cheaper than Grand Prix Audio anything.
I use "sad balls" under my Threshold s450e @~75lbs.
Arbor Scientific - item # P6-1000-03. The refer to them as stabilizing spherers. Also get #11 O-rings from Home Depot to keep them from rolling around on you. You can even cut them in half (a little tricky) and use them as a substitute for vibropods, sorborthene, etc. feet under cdp, preamp or whatever you want to isolate.