Few things I would try. One a DDC for the MK1 is a must. Especially coming from a computer. Get a used Matrix DDC. Then flip from USB to I2S input on the MK1.
You mentioned what software, using roon there are multiple ways to fix and pump up the bass where he wants. PEQ or the harder way with Convolution filter. Its another cost to bear for the subscription, the matrix is pretty cheap used. Cable depends which one you buy. RAL is very good for the price. Not sure if those two pieces of software have a built in PEQ or now. You def want to see if you can fix before the DAC with some sort of filter. HQPlayer is another many here have raved about. I have not used it. I use a convolution filter to flat, and found it flat and boosted the bass with PEQ filter. I posted it in another chat recently here.