Fwiw AVAS, I'm a high-end audio enthusiast as well, and have approx $60K into my home theater. I've got crates of my old 70's and 80's import vinyl, and absolutely enjoy pulling those out, along with my SACD's, DTS, and one off custom surround mixes I've collected over the years I've got on NAS servers. I don't consider myself a snob by any stretch, but I know enough to realize that all solutions require a thorough understanding of the environment, which is often the limitation foundation you need to build from - and is absolutely part of the equation here...
My CVO Harley has 8 speakers and a sub, running over 2,000w, and I've placed in the top three a couple of times in regional competition without really trying. However, on the highway, while loud and clear, it looses alot of the <60-80hz range at speed. But it will destroy your Bose system in SQ and loudness every day. In my vehicles - Cars & Boats, cannot tell you how many stock oem sound systems I've ripped out for aftermarket builds, and surely, I trust you've looked at the quality of the Bose components, right? Pretty much across the board, the number one thing you can do for the best bang for the buck is to rip out all of the Bose speakers in favor of just about anything else. I've tried all sorts head units, amps, speakers, subs, dsp, and other stuff over the years, but I digress. Irrelevant to go further.
The fact is, the thing you are missing is A) the Cadillac Bose system isn't high end by a long shot - Bose induces more artificial processing than any other audio system known to man, and let's not forget about ASM, B) unless you are sitting still, with the engine off, the environment is far from ideal - and diminishes quickly with speed - which in turn, ups the processing even more, and C) the only Remote Portable CD Players available are pretty low end and will provide mediocre output even in the best of conditions - again, when you are sitting still, with the engine off. If you think you are going to get Oppo performance out of a portable at any price, please rethink that expectation. Your options are minimal at best, but you already know that.
Again, if you rip your own CD's at 320kb, and play it side by side, its very hard to tell the difference at any speed over 30 MPH. I'm not saying to make this your ONLY solution, but seeing you cannot find an acceptable (in your opinion) CD Player option, what are you going to do in the interim?? I'm suggesting to Try it, Test it, and continue your CD Player Search. What do you have to lose? Boycotting a first step solution over the guise of upholding your audiophile integrity, while running Bose stuff, is a bit comical. Even CD44 pales in comparison to CD192, but the fact is, you will never hear the difference in anything but a controlled environment, which a vehicle will never be. And for that matter, many people cannot hear the difference in blind tests between CD and MP3-320 in an automobile.
That all said, here's the KICKER. If you open the manual, you might stumble on the fact that the 2020 system will handle FLAC. If you review the entire procedure I graciously shared above, and instead of selecting MP3, select FLAC (Lossless), you will absolutely, without any doubt, end up with a result far better than ANY portable CD player can ever provide at any price point, PERIOD. There is no better solution with the stock OEM system.
Give that a whirl. You're welcome.