Not a liquid treatment, but you could try the Mapleshade iconoclast zapper gun. I find that increases low-level detail.
Another trick I've found on Cds with harsh treble is to use a computer to copy the disc to a black Cd (I use memorex). They seem to work as an equilizer of sorts. This seems to help at the CD transport read process. For me it's as if the treble is "slowed down" so that now, finally, with some CDs the treble timing is in sync with the bass. I know, it's hard to fathom in a digital, bit-perfect world. I'm an MIS professional, but I've come to grips that some of this voodoo does indeed work.