Next upgrade?

+1 @artemus_5  Exactly my thought. Mod that DAC, baby.

@sounasega You sound like you’re in good shape. I really think that speaker, listening position, and room acoustics are the next step. I bought a Umik and downloaded REW software. Using that to analyze the tonality and reverberation in my room -- in conjunction with listening -- changed things dramatically. Dealing with room acoustics is time-consuming and laborious, but are magnitudes more effective at improving the sound. Perhaps those are all factors you can’t change and so an upgrade is your already best path, so I’ll just shut up now!

REW can do many things. I use it to gauge where the frequencies are too high or missing and to gauge reflections. I don't hook it into a system as an equalizer or correction tool. 

SEE: 

@diezahlen  is correct. This is a must before an upgrade.

@sounasega 

Problem is that I don’t know what my end goal is because I don’t have any memory of other systems I have heard in past. I can only use my current system as reference and discern why and how I like the results of changes on the same system. 

In REW, you're seeking a curve that doesn't go too much above or below 6db (to pick a very audible amount) of your input signal db (say 80db).

If it's 6db or more below, you are missing actual notes. Adjust the room, speakers, etc. to get them back in and you will here the presence of notes and other auditory phenomena that you didn't before. You don't need memory of another system to be able to say, e.g., "Hey, there's a tambourine at back left." Or, getting rid of a peak at 80 hz, you might say, "Ah, the strings and fretting of the bass are now clear; before, it was just a puff of bass-sound." 

Does that get you started?