A Low Cost Pleasant Sounding Used CD Player?

I had a couple NAD CD players and have enjoyed them over the years. The last one I had was C 525 BEE. You should be able to pick up one pretty inexpensively.

If you just need a transport, I would not worry about which model; "the sound" of a digital reader is beyond comical. 

As you are budget-constrained, I would focus on gap-less playing (may depend a bit on what you listen to), regardless of whether it is a CD player (with internal DAC) or transport-only. If you like price-look-formfactor of something you see, check reviews re gapless playing. Most CD players have a digital out (check!), so if you want to maximize flexibility down the road, maybe get CD player and use digital out to your DAC.

Another thing to consider is that a "transport" by its very nature is "audiophile" targeted, therefore, likely overpriced for what it is. On second hand market, there are WAY more CD players than transports, which will also have effect on price/value.

I had an old ca. 1986 Sony ES 5-Disc change that got a lot of play until it finally dies around 2003. It was hefty at about 24 pounds, and read discs very well. Unfortunately, it only had a toslink digital out. I remedied that by inserting a $200 Monarchy 24/96 re-clocking device between the transport and a Theta Data Basic IIIA D/A converter, that I bought on Audiogon for $650. From the Monarchy to the D/A I used AES EBU digital interconnect, with excellent results. Shortly after the Sony died of old age, the Theta took a lightning strike. So now I have an Emotiva ERC-4 CD player which is also built very solidly for $600. I'd love to try it as a transport, but haven't acquired a new D/A yet. I cannot say any direct comparisons, b/c I had too many variables in the system at that time, but think the Emotiva would make a great transport only.

I had a refurbished Onkyo 7030 and it was quite reliable, in fact it was from accessories4less also. Then I bought a Rotel CD-11 Tribute and prefer the sound from Ken Ishiwatas creation. Never had a problem with either CD player and their at reasonable price.

Look for refurbished gear. I have a Yamaha CD S 3000 refurbished.