I will second the 14mm Funk Firm Achroplat. I put one on my P3 a few weeks ago, and the noise floor has dropped through the, um, floor, compared to the glass platter. I now know a lot more about what's actually on the records I listen to. Also bass is much improved in quantity and quality. What I think is going on is mostly a deletion of distortion across the audible frequency (whose presence I didn't recognize before getting the Achroplat). Recordings of string sections and choirs sure play a lot cleaner, anyway.
How do you like the Clever Clamp--does it grip the record okay? I've been thinking about a weight, since the Achroplat weighs about half (or less) what the glass platter does. Haven't seen any (weights) that really excite me though.