06-16-08: TvadTrue dat. I've gotten some of my most significant improvements in clarity, jump, inner detail, and dynamics from isolation. In my case, I have $20 in PartsExpress/Dayton threaded brass cones to replace the feet, a $25 butcher block cutting board from Ikea, and Vibrapods I had lying around the house.
...I'd recommend putting the money toward isolation for the table.
If I had a little more to spend on isolation, I'd get Mapleshade brass cones and maple board or KAB's Isonoe threaded feet. Then there's the Gingko Cloud as another viable option. I definitely got a big improvement moving to a less resonant, more rigid rack (that was actually less expensive than the welded steel rack it replaced).
That $45 probably wrought the biggest improvement overall. It also creates a better baseline for hearing other improvements, such as better cartridge, headshell, fluid damper, etc.