JLM,
You're right, I should have been clearer that I haven't actually heard the Underwood Hi Fi level 1+ mods to the Onix cd-5. I am basing my opinion on the description of the mods on Underwood's web site and Audiogon ad, the review of the same mods on the identical Music Hall 25 in Six Moons awhile back and the opinions expressed in some online threads that are probably as unreliable and second-hand based as mine.

Seriously, the Apollo is a great player, which I agree is well beyond the others mentioned stock. However, I have heard both the Apollo and the Music Hall 25 (and 25.2) and I chose the cd-5 and am going for the mods because I believe that's the best bang for the buck, but ymmv.