what is the best, least costly DAC...?

Look at the Musical Fidelity V-DAC. Very good in stock form and better with the "Little Pinky" power supply. I think it does what you want but as I don't do computer music I can't be sure.

If your V-DAC sounds dull and lifeless then I would suspect the digital cable or transport. I admit that it makes little sense to use a $1700 digital cable[Transparent Reference] with a $300 DAC but it works for me. I have found that the cable makes a very considerable difference. HIFICRITIC has tested both the Saturn and the V-DAC, they gave the Rega a score of 29 and the V-DAC 42. For comparison the Benchmark DAC scored 22, the V-DAC got just about the same score as a very expensive DAC from MSB which is close to $10000. They think it is one of the best buys in audio.

I suspect that the problem was the Mac components; my friend used a Mac 402 with matching Mac pre driving his Wilson Sasha speakers until I took my Musical Fidelity NuVista M3 over, they were gone within a week. Since I do use Musical Fidelity components in my own system [ Kw line stage, Kw phono stage, M3 amp, V-DAC] I think I have a better idea of what they can do. I regularly compare them with other components I have like an Audio Synthesis DAX decoder, or Conrad Johnson Primer 350 amp and they come off very well. The M3 is not quite the equal of the 350 but it was half the price, includes a pre section and will drive loads the CJ won't.

Trebejo, I wish I was as smart as you and could know how something I hadn't heard sounded. After 50 years in Audio I have learned that the SOUND and not the COST is the important thing. Is what I am using logical? No. Does it sound good? Yes. Do I recommend it for everyone? Of course not! I was describing the sound I get in my own system. I paid $700 for the Transparent, a totally ridiculous sum for a piece of wire; but the system sounds better using it. Should I only use it with my other DAC, a much more expensive model? My point was that the V-DAC is not embarrassed in fairly high end company; my system is posted if anyone is curious.The V-DAC received the same rating from HIFICRITIC as a $10,000 Dac from a high end company that is highly regarded. Perhaps with more experience in audio you will learn that insults are no substitute for knowledge.