Can I use a variable output CD player in a very high end system to connect directly to an amp and avoid the preamp and still get the same sound quality as though there were a pre-amp? If so, are there only certain CD players that would work?
Yes, provided that the CD player's output section was designed to drive an amplifier directly (one would assume that a player with variable output has that capability).
In my experience, bypassing the preamplifier is a good thing—the best preamp is no preamp. All preamps degrade the signal, and removing one from the signal path should result in cleaner sound. This is provided that the CD player can adequately drive the cables between it and the power amplifier. It helps if the power amplifier has a highish input impedance (greater than 20k ohms).
The drawback is that you have no source switching, which isn't a problem if CD is your only source.
What are current high quality CED players that have variable outputs? Is a 10:1 ratio of the amplifier input impedance vs CD output impedance a good match? How else do you match the two?
A 10:1 ratio between the CD player's output impedance and the power amplifier's input impedance is an absolute minimum. The primary criterion is the CD player's output stage—whether it can source plenty of current. This is less of a factor if you use short interconnects, and if the power amplifier's input impedance is high (50k ohms, for example).
What price range are you considering for a CD player?
Up to about $2000. How much is "plenty" of current. The Quad 99CDP ,as reviewed in one magazine, was not impressed with the variable output. I don't know too much about the Vincent CDS6. Any recommendations at all would be appreciated. Why don't more people set up like this?