Mapleshade SilClear is an amazing tweak! One small jar will last a lifetime and the difference in clarity, detail, and overall smoothness is nothing short of spectacular, and I was using Caig Pro Gold before but this stuff takes it to another level!
Another great tweak is to use Exact Copy to record CD-Rs with your computer system. The new copies sound much better as noted above and Exact Copy does a much better job than Roxio or the other duplicators.
However room treatments and setup detail make even a bigger gains in a high rez system. Try some Vibrapods and Vibracones. This is one great combo that doesn't cost a bunch either.
