What high-end cdp for low-end quality CD's ?

What does it mean "the best darn you can afford"?
Does that mean that if the budget is $20k one should go for Burmester??
There are lots of tricks with digital audio to make it sound different. Heavy clampings, tank-ish constructions, hi-res pics taken from the development lab it's all all to grab your pocket without substantial playback improvement and investing onto it therefore should be very limited.
The price of a raw materials on CD-players that are mostly ICs is getting more cheaper and its quality increases with newer more precise tech-s applied. Hence the price on the digital playback at least should not increase and there should be lots of possibilities getting less costly unit with greater performance. Another way to vary the CD-player performance is playing with feedback levels. At different settings the output will be lower or higher along with the different responce to a load and freequencies. Certainly the deeper feedback will have more linear responce and lower output voltage. This combination of feedback and output voltage on digital playback can be quite differently "interpreted" by further amplification components that as you may know have also different feedback, sencitivity, input impedance, etc etc... characteristics that may or may not by in SYNERGY with your source.
Tube output is a special case that can be applied to any CD-player so the meaning of "tube CD-player" should be considered as misconception or another trick to involve marketing since it's just a pair of dual triodes in inverting differential connection that inverts phase 100% i.e. giving 100% local negative feedback stage. This buffer you can add-on to any CD-player just by simply buying <$100used Musical Fidelity X10 tube buffer that no doubt would act on poor CDs and cheap CD-players quite beneficial.

To my personal knowlege Dennon and Pioneer are the brands that use THE latest models of chips and have highest standards for the digital playback. You will never overpay if you shop arround these components and in case of bad recorded CD you may add-on Musical Fidelity X10 buffer or Equalizer and turn it off whenever you don't need it for the good ones.

I'll take some exception to the general recommendation of "buying the very best you can afford" and spending your wad on a digital front end. I would first make sure that the differences between what is available in $2000 price range that is abundant with damn fine players (even less if you buy used) are both perceivable, and most of all worth the added $3 grand to buy some more-state-of-the-art $5k unit. Though it may sound better to you, it also may not at all, and then what a waste of scratch that would be!

As far as making bad recordings sound better; I'd agree, no CD player is going to accomplish that. I've recently gone over to a quite wonderful Wright-Sound AG1000 preamplifier (from his dealer line). That unit has 'tilt' controls for 100hz and 10khz. They have a bypass switch as well. These are not 'tone' controls, but 'tilt' controls - someone more smarter than me can splain how they differ but my poor understanding of such things is that tone simply boosts or lowers the specific octave, while tilt actually 'tilts' the spectrum around that octave...did I get that right?. I've found that I can do some bit of fudging that will definitely improve the listenability of some poorly mixed recordings and make them much more enjoyable than they were with a pre with no such controls. They've worked brilliantly on several bad recordings I've tried them on. I don't know which other high-end pre's offer this option, but it may be a better way to address the problems you wish to solve with a better front end. I can highly recommend the Wright pre as an outstanding pre as well.

Marco

Try Electrocompaniet for the most liquid and smooth sounding player I have heard. I own a Simaudio Nova which doesn't make terrible CD's sound great, but for example it allows me to listen to bright 80's pop cd's like David & David or Genesis without running for the door.

Marco, I disagree with your assessment that no player can improve the sound of a poor digital recording. The Audio Synthesis DAX Discrete certainly makes a lot of CD's more listenable. Like you, I am technically not up to the task of describing why, but I will assume that the DAX Discrete accomplishes this, in part, with over the top oversampling.

You mentioned your Thiel 3.6's. I have a pair also, and have recently moved to a dedicated room with 4 dedicated power circuits. While I am hearing new details and clarity, I (and especially my wife) am being irritated more by the edginess of the Thiels. I have an Arcam FMJ 23 player. I recently auditioned some Martin Logan Ascents and some Sonus Faber (Cremona Auditor and Grand Piano) and was very impressed. So, you might consider focusing on the speakers vs. the CDP. Good luck and keep us posted- I am in a similar boat.

Bill