Next tweak to buy?

Perfect: Check out the thread "shelf material", lots of info on Pods and Cones.

BDR cones - without a doubt!

P.I., something to consider as you begin this process is that many tweaks make your system sound different, but not necessarily better. That said, I second BDR cones as a good place to start. Enjoy!

Audiopoints at audiopoints.com is an alternative to BDR, and are about the same in price. The thing with the audiopoints though, is that they make threaded versions to screw in to your components, but three 'cones' or 'points' are known to be more effective than four. The audiopoints are made out of brass which is one of the best materials to transmit energy. I don't know about bdr. I prefer to use materials that pass the vibrational energy from the componenet instead of using dampening material such as sand or pads that absorb it.