Best DAC for PC audio direct to amp

Here's what I'd suggest, and it's an "out-of-the-box" suggestion.

Look for a used APL Denon 3910 with digital input option (coax), and the H Attenuator option. Almost all of the later APL players had these options. The H Attenuator (or hybrid attenuator) is the option that allows you to use the player direct to an amplifier. The output is tubed. It has a remote volume control. It sounds incredibly good.

The APL DAC is frankly the major portion of the player, and at present used prices they're almost being given away.

As long as your computer source has a digital coax ouput, you're in good shape.

Benchmark DAC1 is dynamic with good bass punch and nice clarity. It is good value and has a good reputation for handling jitter with plenty of reviews on it. Sure it is an EBGO DAC (Everybody's Got One) - so no special pride of ownership - but if the sound is all you are worried about then it is a solid choice.

Bel Canto DAC 3!

Get a USB to S/PDIF converter (Trends, Hagtech, etc) then feed to Audio Note DAC to whatever budget suits you. Even their lower level models are incredibly dynamic and musical. May help to have a jitter reduction device before the DAC as they don't reduce jitter internally. I know I've now suggested three boxes instead of the one that you seek but it would be well worth the trouble!

Get the Berkley. Robert Harley of Stereophile says that it performs even better than with a preamp in the system. Plus, it uses a "long-filter" which is similar in performance to Spectral Audio's top-sounding CD player, the SDR-4000 pro. For the money, this piece is a giant-killer!