In addition to the rubber and cork blocks, two other cheap alternatives to try are Parts Express brass cones ($25 for 4) mounted to, e.g., a cheap wood cutting board (try IKEA or whatever -- any kind of wood will provide significant vibration absorbtion) or, for a different flavor, Vibrapods (about $5 each).
I keep a bunch of each (and other) cheap tweaks around to try with equipment. Unfortunately, for most setups, trial and error is the only way --and to me, trial and error is only made tolerable by inexpensive tweaks. I couldn't imagine doing it with hundreds of dollars of boutique carbon fiber cones etc. With the cheap tweaks, even if it is only the placebo effect at work . . . it still works at a reasonable price! After all, this is a hobby, not a physics experiment.
I do have to say that I use an expensive air suspension stand for my turntable (Arcici), but this is only common sense when footfalls and closing doors obviously transmit unwelcome vibrations to the tone arm and cartridge. I also use inexpensive air suspension platforms for, e.g, tube preamps, because you don't need an engineering degree to figure out that vacuum tubes are all, to some extent, microphonic, which means any isolation you can give them from common household vibrations (footfalls, closing doors, refrigerators, furnaces) will help keep the noise floor down. Again, this is a hobby, so it is supposed to be fun! Experiment!
One other example (computer geeks will think it silly), but I put my big (terabyte) hard disks on a big pad of foam rubber and a wood base on top of the foam. May not make any difference to the sound, but it sure as hell cuts down on the mechanical vibration from the drive -- it turns an audible whine into silence.
Regards, James
