Good Inexpensive DAC/AMP with digital volume control for HD600

I'm looking for a DAC/AMP for a very specific situation. Basically it will be used "professionally" but not for music production rather for noise engineering work and doing playback analysis. Basically this means I'm not really concerned with getting the absolute greatest in possible fidelity a lot of the content won't really extend beyond 2-5kHz.

However what I do need is to be able to drive HD600s well and also importantly to have a digital volume control that ideally reads in dB so that the output level can be calibrated to get accurate playback levels. Being limited to 24/96 would be perfectly fine and input will be usb. The obvious "professional" choice for this would be something like an RME ADI-2 DAC FS and actually right now on a setup like this we have an RME Fireface UCX being used only as a DAC feeding a 5 output B&K headphone amp. But this seems overkill for what is needed in this case so I'm looking to cheaper alternatives.

Here are some of the options I have found and am considering so far:
Topping DX3 Pro+ (only has 3.5mm output, 1/4" would be preferred)
Topping EX5 MQA

I'm hoping to find something even less expensive and simpler, ideally with 1/4" output, but it seems like requiring digital volume control is really limiting my options. Is there anything I'm missing that I should be looking into?

 

I couldn't afford a proper amp (next computer will be an M1 Max or M2 Max 16" laptop, which I hear doesn't need an amp) so I connected my HD6XX headphones to a cheap used Yamaha receiver and it has a digital volume control in dB. I leave the computer volume maxed out. Novice ears, but it seems to drive them a lot better than my laptop did.

Edit: I'm feeding it with a cheap DAC with RCA out.