There have been numerous threads here about CD tweaks/treatments like Auric Illuminator and Optrix. I use the Illuminator and really like it; am not familiar with optrix but know that there are many out there who are very positive on it. Here's a cheap total system tweak I read about on Audio Asylum a couple of weeks ago. Go to an auto parts store and buy some dielectric tune up grease (from $3 to $15) and apply a fine film of it on all power connections (DO NOT apply to signal connections such as spades, bananas or interconnect RCA's!) such as prongs on male ends of power cords and female iec's (just use a q-tip or toothpick to put a little of the grease into the openings and connect up!). This supposedly helps to maximize electrical contact and prevents arcing etc. I thought the result was pretty good in terms of quieter background, smoother delivery of the music etc. In my opinion, much better than XLO's TPC which Jonathan Scull raved about in Stereophile a few years ago. A nice cheap tweak!
CD other tweaks
Over the week-end, I had the chance to try an audio tweak.. sanding the outside rim of a CD, the impact was great. I have tried the paint route and had some success..but I had heard about using very fine grit sandpaper on the outside rim of a CD. I tried it and it was up there with major component changes. The most hear-able differences were: a more quiet or "blacker" silence between notes..and a sense or more detail..but more ease at the same time. Has anyone else tried this?