otherwise there is the question of what audio you need to play?
The Oppo 105 plays CDs quite well. It has excellent power supply and analog stages. However, one of the problems is that it is designed as a "universal" player and doesn't have specific digital clocks for CD playback. Also, it does still have a switching power supply for digital section (which can be upgraded to linear from OPPOMOD).
There is a used Sony DVP-9000ES for $314 that will likely sound much better for CDs, as it is specifically designed for 44.1khz playback. However, it is extremely old and could be prone to failure.
Try hunting down a Jolida tube CD player? I have also read that Rega CD players are very excellent as well.
So, the question is really:
"Best CD-only player for $700?"
R2R ladder DACs have only recently been displaced by other types, so besides reliability questions, the SQ question is what is the best Ladder DAC based CD player...
The easiest thing is to buy an Oppo - it will sound very good or better and can be returned if you don't like it.
Brands to think about for $700 max would be:
Denon & Marantz
I like tubes, but I keep them bottled up inside my pre-amp....
If you're after the best choice CD player, you'll probably get better sound from a dedicated CD player. If all the money you're paying is focused just on audio, chances are it will be better than a universal disc player.
That said, I have an opportunity 105 and I love it. I use it as a file player as well and just today decided to mess with tidal. It also replaced a cheap DVD player and Yamaha CD changer, so it tidied up my rack and sounds loads better
You have some older, but very good equipment. Your system deserves a real CD Player. I'm currently using a Rega Saturn-R and love it, but it is out of your price range. Although I have not heard it, my understanding is that the Rega Apollo-R has a similar "house" sound. For under $700 used, it may be a good option.
I would suggest considering an external DAC and use your CD player just as a transport. If your DVD player dies, then replace it with another. Most people are wary of buying a 10-15 year CD player, but a player that cost $5,000 15 years ago can now be picked up for $500 (or less). There are some terrific bargains to be found, if you keep your eyes open.
I bought a 15 year old Sony S9000ES and played it for years before selling it and buying a used 10 year old Esoteric DV50S for $1,000 ($8,000 new).
There are some very nice DACs to be had in the $700 range (both used and new).
These are just two examples. There are lots to choose from.