What CD player will warm my Thiel/Classe systm?

This Onkyo CDP--it's a garden variety mass-market CDP like you'd get at Circuit City? If so, it may not be that your system needs more "warmth" as much as it needs to get rid of harsh or brittle "bad" digital sound. A used Cary 303-200 would do that for maybe $1200. Or a used Meridian 506 for maybe half that.

The bass is probably a separate issue. But if you listen mainly to CD's, & you have a mediocre CDP, "more bass" may not increase your satisfaction that much.

I'd say focus on a good CDP first, then maybe a good equipment rack. A used REL Strata III sub for maybe $900 might be a good idea later.

I totally missed this: "My room is about 20 x 30 with a high ceiling."

When I first started getting into "high end" audio, about 10 years ago (after years of owning a NAD/JBL "mid-fi", to be generous, system), I bought drastically better speakers, slightly used B&W M802SIII's. I then spent a few years (in retrospect, needless) frustration as I was so clueless about how much power they needed, among other things. Many visits to various "high end" audio salons in the metro-Boston area were almost less-than-useless in figuring out what other components I needed.

I still think you should consider upgrading the CDP--I can't imagine a 10 y.o. Onkyo is doing justice to the Theils & Classe amp. Seriously, I think a Meridian 506 for $600 perhaps (?), or a new Jolida would improve your system a lot for low$$. If the front end is mediocre it almost doesn't matter what else you do IMO.

The good news: a used sub & excellent used CDP might run you $2K roughly for both.....