Can a DAC sort out a flat\cold amp?

I read an online review that described the 1200’s bass performance a somewhat lean combined with forward mid’s/high’s, but didn’t search for other reviews.

Have you tried the tone controls (either backing off on treble or adding bass (didn’t see a tone control defeat in the pics)?

Don’t know if makes a difference, but per the pic the power supply of your CPU is really close to the bottom of the 1200 (assuming that it and the fan are located @ the top/back of the CPU).

Unless your current DAC is very thin sounding/bass shy I can’t imagine another DAC remedying your situation much - if @ all.

Can you try an inexpensive, but decent subwoofer (maybe borrow one)?

DeKay

You might want to consider trading YH 1200 for a used Hegel H90 with some money left back to your pocket. This integrated amp is equipped with more than adequate DAC/Stream which allows you to play music directly from Hegel. It is a very wonderful thing because the desktop music playing is like a third rail. It has only 60 wpc but high current with damping factor more than 2000 which should drive your speakers with authority and clean bass.  

IF you desire more power, a used Hegel H160 will just cause you $300-500 more than H90.  See the review by https://www.youtube.com/watch?v=F2iLYRjCFOw&t=1156s.

+1 On double checking speaker phase. I know it’s basic but this is a new hook up?

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.