Recommendations for used CD player

I'm looking to improve my sound by adding a CD player to my system.  I'm currently now just using a Yamaha DVD player along with a Yamaha Aventage home theater receiver (which uses ESS Technology ES9006 SABRE DACs).  I use the receiver as a pre/pro with a Threshold S500/II amp and B&W 802 Series 2 speakers.

Right now I really like my sound and I've read these DACs are fairly high quality, but wasn't sure if I could get improved sound by adding a used, higher end CD player and possibly outboard DAC.

No SACD needed, my budget is about $400-500.

Thanks.