My experience is somewhat similar.
I don't use the dac in my Pro+. It's ok, but not as good as my Nuprime.
I find it's functionality as a streaming source switch is very handy and clean, but the room correction is a real godsend.
My room has always had a problem swallowing and muddying the lower mids through the low bass range. I've tried many fine speakers in my room, and this is an issue for all of them, including my current all time fave, Avalon Opus.
This cheap device has improved the problem dramatically, with no downside for me.
Now the bass is deeper, much tighter, and stronger, and the balance below 250 hz. is excellent.
I started with the automated correction first, then tweaked the results by ear. Usually my settings end up within a db or so of the automated one.
Very cool results for little $.
If, like me, you can't do extensive room treatment to correct the room, this little guy is worth a look. The more expensive model mostly just uses a better dac, which I don't need.