Improve sound

I think your DAC is fine, the least problematic. Your amp is OK, but does it work with your speakers? Start with a small change, bookshelf speakers. Look for music that you love and listen and look for sounds that blow your mind and make you want to turn up the music. You need a baseline, something to strive for and it seems you have been feeling "meh". 

I know nothing about your amp but it's safe to say, it's for home theater/entertainment and not for peak audiophile joy. 

The short version is: you have to learn about yourself. Neither your speakers nor your amp is audiophile, maybe midfi, if you sell both and add $500 you will have a lot of options ($2500?)

You can get a Parasound 23+ ( assuming used) for a $1,000?

Upgrade the room first. There's always something you can do to improve the room. It plays the biggest roll in the system's sound signature.

Many here know this but really hit a wall (pun intended) and never fully exploit the room's potential, myself included.

I learned by sheer accident after years of believing I had done enough. 

Room treatement is the most important upgrade for electorstatic speakers. Since I have owned ML  -> Quad -> Stax -> Sound Lab A645, I think that I have some experience with this subject. 

The room acoustics and the setup are the biggest contributors to the sound you hear. If they're not right, no gear change can help that.