Should I make any changes?

Aesthetix CD player DAC preferred Signature or better Eclipse level or you could do those upgrades as $ allows. Also very responsive to Tube rolling… Mullard and Amperex.

full disclosure I have the DAC version in Signature 

enjoy the music

Apogee are something special, glad you had serious time with them. We have a small pair in our sitting area. A friend has Caliper Signature heavily modified. Fun

This is probably the appropriate time to move over to streaming. It is replacing physical media as the mainstream source of music with as high a quality or better sound quality. Also for nearly no cost ($12 monthly) you get access to millions of albums. Quboz has well over half a million high resolutions albums. I'd look at this as the perfect opportunity to make the jump. Don't worry about the sunk cost you have in CDs... well, it's a sunk cost and virtually all your albums will be available on streaming. 

Invest is a streamer only as you would any other components. You want to equal or best your DAC to get the most out of it. For you I would recommend a used Aurender streamer to get the most out of your money. Like a used Aurrender N200.  Like many of us, after we got a streamer that sounds as good or better than CD and or vinyl your whole world of music enlarges and you don't look back. 

@thecarpathian 2 minutes can feel like eternity.

And "more" is right, you probably need to spend 40K for a decent streamer and DAC.

Room treatment, and maybe even a quality subwoofer?

I would recommend on the Teac/Esoteric CD player/streamers.  They are above your stated budget, but you might want to stretch for one.

I liked the Theta converters, but by current standards they lack openess and transparency.  IMO, not a critical flaw.  Doing nothing isn't a bad decision.