DAC recommendation for an entry level system

I would like to add an apple TV a Logitech Squeezebox Touch and a Dune HD Prime 3.0 blu-ray player to my system which consist of NAD C375BEE Integrated amp, Rega P3 24 and Revel Concerta F12 speakers and would like to know if anyone can recommend a DAC. I have my music collection ripped to FLAC and Apple Lossless on my server. I can go up to $600 and I'm willing to buy used. TIA
For USB only I recommend the HRT Musicstreamer II+. I use this in my tubed system and it sounds wonderful.
Thanks for the recommendations. Ideally I would like a DAC that has Coaxial, Toslink and USB inputs. I'm considering the new Musical Fidelity V-90 DAC and also the Cambridge Audio DACMagic 100. The Maverick TubeMagic 2 DAC.
I head the Dac Magic with a Krell integrated and some Soinics speakers...really liked it. I've owned a PS Audio DLIII for many years and got a lot of enjoyment from it. Great build quality.