Welcome.
In the fast changing world of DACs I'd avoid older models as being completely obsolete and not cost competitive. Don't bother with anything 10 years old., besides caps age could soon need replacing.
It also depends on the quality of your library. New DACs can reveal the warts on older CDs. I home auditioned a $1300 Schiit Gungnir Multi-Bit (balanced design) a year ago and it made 10% (the very best audiophile recordings) of my collection sound better but 30% (music I love mostly from the 70's/80's but poorly recorded) sound worse. Sent it back, as I want my system to serve my library.
NOS (Non-OverSampling) DACs are very smooth, to the point of putting one asleep IMO (limited dynamics/detail). Do you have interest in higher resolution formats (they get a lot of press but sources are limited/expensive)? Had a $500 Emotiva DC-1 balanced DAC/preamp/headphone amp, the opposite of NOS sound, but rough around the edges. Then moved to a $900 DSPeaker Anti-Mode 2.0 Dual Core, another small balanced piece (DAC/preamp/bass DSP) that sounds better (compared to the Gungnir MB) but has an really cheap remote that I'm still using two years later. I like the Schiit approach of upgradability and no nonsense design. The Schiit BiFrost MB (single ended) is only $599.
iFi has a following around these parts, but no remote, too tiny for me (dip switches), not balanced design, limited flexibility, and based on a stop here on a tour of the iTube2 - color me quite unimpressed sonically.
Check out audiogon.com. Pre-owned DSPeakers are available for $500. Benchmark DACs are solid. Saw some Hegel, Bryston, and Mytek DACs there for under a grand. Also saw an Auralec Vega for $1500 (over your budget but a wonderful piece).
