I have applied Dynamat on the inside of my transport (sparingly, a little goes a long way) and have used Blu-Tak on the "Bridge" of the drive and on the drawer. This gave noticeable improvement. But what was my best tweak, and seemed like an upgrade in equipment, was using Blu-Tak on the clock and on parts of the PCB in my DAC. Some prefer using a small sandbag, but I chose the Blu-Tak. Go to AA and look up "Sandbag on the clock" or “Damping CD players” or try this link
http://db.audioasylum.com/cgi/m.pl?forum=tweaks&n=30356&highlight=sandbag+on+the+clock+tweak&session=
This is a wealth of info and you can read about the differences between sandbags and Blu-Tak. I never used to be a believer in the isolation idea, but after this tweak, I'm a TRUE believer. It was absolutely night and day. It is now cleaner, detailed, better sense of depth and soundstage and the bass has improve.
Another worthwhile tweak is to find a good way to isolate the transport and DAC from other vibration. For my setup, solid maple shelves (1 ½ inch thick), on Vibrapods and cones between the transport/DAC and the shelf. I know this is a highly debated issue, but only you can decide for yourself, by experimenting.
I also agree with the others on trying different power cords, especially on the DAC. If you can have a dedicated circuit put in, get one for your digital gear alone, (along with the analog side as well as for your amps, but that is a different matter) which will also help. Hope this helps. Just try some of these; you just might like what you hear!