Can a DAC sort out a flat\cold amp?

For a solid budget DAC I'd recommend a Maverick Audio TubeMagic D2 for about $300 and then eventually upgrade it with three Sparkos Labs Dual Discrete OpAmps SS3602 and possibly roll in a tube for some extra fun.

For what it's worth, seeing your room made my head hurt because it looks to be very tight quarters and also very live which could explain what you're hearing.

I've seen a number of reviewers state that the Yamaha's top end calms down considerably with enough break in time. You Tuber Sean @ Zero Fidelity did a video on this, if I remember correctly.

OP, I do second your consideration regarding a DAC.

I can imagine that the audio interface (which is primarily for home recording and/or dj-ing as far as I know) is, for some reason, the weak piece. IMO, it's not the amp nor the pc.

In order to test, you might want to invest a little money in a decent DAC (no need to spend more than 200 Dollars, really), using USB 2.0 and a media center software (if you don't have 1 alreaday) like jriver or foobar (no additional $$ investment for fb). That is what I would do if I were in your place.

Even without a change in the current lineup of all your gear, you should hear a difference in SQ. Although I do support the respective suggestions of other members of this community, which will further improve SQ.

Please comment on the results after you have changed whatever you intend to change. I'm sure all those who have contributed to this post will appreciate it.

Best, eagledriver

If the sound is cold, I would first go over the power cord that I use for the Amp. Just try different power cables, don’t buy first ask to try. After that if you like it, buy. Most probably, this will solve your issues.

First of all I would not pump any more money into this set-up.-which is being used as a work station and a defacto hi-fi set up

Your aim is to improve the sound of what you have at minimal cost.

I would replace speaker cable and inter connects though.

I would also lose the table , display and keyboard , electric fire , flip flops and any other clutter. Use headless control via mobile phone.

Get the speakers away from the walls.

The PC it looks ancient and may have a limited speed cpu ? - Replace HD with  SSD if not already done.

A clean Install of windows server 2019 - Free trial available Reduce number of services running in back ground.

Remove as much clutter on SSD and install HQPlayer -free for 30 days. Employ highest HQP settings that the cpu will permit.

Pull CPU out and replace with quality  thermal paste 

Install ROON +HQPlayer

Ethernet connect from router to pc -disable wi-fi