Mark Levinson 336 vs Pass Labs X350?

With my Nautilus 802s the Mark Levinson is a much better match. With your Thiels it may be different, you'll need to listen to both of them in YOUR system. Make sure you demo fully broken in amps - without a proper break in period they won't sound their best.

I agree with Mmccoy regarding CD players, for the money the CD55 is tough to beat.

The CD player is superb, I would not change that. Look into isolatin/damping for it, as it is somewhat lightweight.
I have no input on the amp choices, both are great.

Both amps are very good. My tastes lean more toward the Pass X350. The presentation is a bit different than the 336 and it seems to be a bit more natural. Niether would be a bad choice.

As far as CD players, save for the Audio Aero Capitole 24/192. From my comparisons, it is currently the pinnacle of PCM digital. One of the special things about the unit is the remote driven volume control. I have taken out my preamp and the sound was greatly improved. If all you use is digital, you could probably sell your preamp and CD player and improve your system with little or no out of pocket expense.

For the CD player I would go to Resolution CD 55. For the amp compare the new Bryston 14.