Modern CD player that has good sound quality

I think the newer cd players sound better, plus they have G-protection and are more compact/better looking. Don't they use more up-to-date electronic circuitry?

Get one with an optical out and feed it to a decent DAC.  The older ones are better made, more metal, less plastic. Newer ones tend to be in better condition and tolerate less than perfect disks. Most of the issue with the recent portables lies in sub-par line out / headphone outs.

I have a Asian market DEJ-01 I bought 8 years ago and feeding it into my Gamma2. Sounds great to me. 

The sony's line outs sound a lot louder and effective than Panasonics.

I'm not very familiar with them. Hopefully a PCDP expert will chime in here. A safe bet would be the last audiophile cd walkman's made by Sony: 

D-EJ2000, D-EJ1000, D-EJ9XX, D-EJ8XX. When you fine one just do some research as there are model numbering inconsistencies as well as different models for Asian and the rest of the world.

A lot of the later lower end models had the built in amp crippled to "protect" people's hearing, so they may not be able to drive audiophile headphone's efficiently.

EDIT: Found this neat link: http://forum.lowyat.net/topic/1257830

I'm not familiar with the sound qualities of the current PCDPs that's on the market today but can recommend some of the younger vintage PCPDs with line outs. The D-EJ2000 and D-EJ01 is a good choice as it has excellent sound qualities with line out. However, both can be expensive as they are sought after by PDCP collectors willing to spend some money. Other recommendations that might not cost as much but also offer good sound qualities with line out would by the Sony D-NE1, D-NE-10, D-321, and D-465.