How many are using Amp to CD with variable...

I can't really grasp what it is that you are asking about.I can give you my experience I had when I ran my Cary CDP-1 like this while fooling around with my system one afternoon.I can bypass the preamp section of my integrated and run it as a power only amp.It sounded okay,but no where even remotely as good as when I put the tube preamp section of my Rogue Tempest II Magnum back in the signal path.There's just something special about the Sylvania JAN 6SN7WGTA and Amperex 7025 tubes in my amp.All I can say is,you know the sound you like and when you get it,you're there!!!!

I am using passive preamp in my system, works very well. There was just a thread on this in the last few days "Why do preamps improve sound of CDP?" It is a matter of taste and system.

I've tried running my Audio Aero Capitole CDP direct thru my Plinius SA-102... however, I found the sound to be significantly better when run thru my Calypso preamp.

I do. I use a Wadia CD player with "volume control" and adjustable output levels and plug directly into an amp. Wadia recommends this, an I concur that it results in more detail and less haze in the music. I.E. better. I use a SS Amp from Classe and have not had a problem. I tried this with a tube amp (ARC VT100) and I think the amp ran hotter. I don't know if the VT100 is an imped. mismatch or what or something to do with the balance XLR pins. i was only doing this with XLRs, because I need real long cables and have tons of XLR stuff.