Best Tweak???

Another vote for the Neuance shelves. They work wonders especially under power conditioners. Another tweak would be to separate all your cables and lift your speaker cables off the ground.

removing the split glass doors from the front of a wooden rack was among my most startling & unexpected system enhancements. Whether they were closed or open, those doors caused some significant degradations

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Symposium Rollerblocks....simply amazing. Go for the grade 3 tungsten cardbide balls option. Try one set under your CDP and then try your pre-amp, power conditioner and amp...It will be quite a surprise.
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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.

I'll go with the CD-Rs on computer with Exact Audio software you will even get CD Text. Good quality disc are important. Fuji has changed suppiers but you can still find the ones that are made in Japan, they are High Definition Burn Certified and are made by a company called Taiyo Yuden which is a leader in this industry. If you can't find the older Fuji's no problem it seems Maxell has also changed suppiers and are now made in Japan by (Yea you guessed it) Taiyo Yuden and are HD Certified. Just make sure it says Made in Japan. NOT TAIWAN! You won't find anything with the disc that says it is HD Cert. but i have software that will read them. There are a few other good ones. I could post later if anyone interested.