What to upgrade next.

Oopwah - Has a good point. I believe you are referring to Dbpoweramp which is what I use to rip my CDs to computer.

I only buy CDs, I only download music if I just cannot find it on CD. Dbpoweramp converts it to FLAC, so I have a lossless copy and I have the CDs as backups.

Then Plex is my player, nothing like browsing music on a large screen TV. Select what I want and play. I occasionally use DLNA from my Oppo or preamp as well.

Will

Since you like both music and movies you could keep what you have and perhaps try different speakers, get a streamer like people have mentioned.

You could also look at a preamp with Home Theater bypass. I have a full home theater setup for movies but like music just as much. I was considering getting a additional system just for 2 channel music but another option would be a preamp with HT bypass. That way I can combine both systems.

If you are able you might try connecting your receiver and computer via network cable and then try your music through HEOS, you might notice a improvement in sound quality.

Also I would personally try one new component at a time, that way you will be able to see how much of a difference it makes. That is a little hard to do when adding 2-3 new items at a time.

Will

Dadork,

I have prime, it comes with Amazon music unless you mean the next level up for music.

I occasionally download a song but I prefer buying CD Albums over a single or downloading a album. Could be a ocd thing.

What is your main focus? Music? Movies? Both?

Your Denon is for home theater, movies so if your emphasis is on music you will have to do something about that.

Your ordinary desktops are not the best for streaming music unless you have a linear power supply, good hdmi cable. Computers can produce a lot of noise and like you said you have a lot of fan noise.
How are you streaming, wireless or cable?

That being said I use a Intel Nuc running Plex as a music server, though I have not done it yet I can get a linear ps and good hdmi cable for it which will make a significant difference.
I do not know why you are having the Windows glitches, I am running Win 10 with Plex and have no issues.

Your bad copies of MP3s are definitely a sticking point. And what do you mean being replaced to HD audio files? Replaced how? With what?
I rip all my music to FLAC from CDs, the MP3s that I do have I am replacing with CDs.

Will

Oopwah - Sounds like we do the same thing, buy CDs and rip to flac using the same software. The computer with Dbpoweramp is currently packed up since I am moving, do you know what bit rate it converts CDs to flac? I know you can also choose the compression level but I can't look at the settings right now with it being packed up. I am curious what the rate is compared to what Dadork is downloading.

I run into the same thing by the way as far as so much content and I do not have as many CDs as you have. Fortunately it is so nice being able to scroll in Plex to view your music, plus I have 15 Play lists I created.
I listen to the radio all the time in my car, so that is how I come across new music.

Dadork - With all your downloaded music you need to make sure you are backing it up to an external if you are not already. The benefit with CDs is that is our backup, even though I also backup to an external. But if my drive with all my Flac on it were to go poof, I still have all the CDs.

As far as 2 channel. I believe when someone refers to their 2 channel system they may also have a sub, maybe someone else can clarify that. That being said I rarely listen with my subs to music in 2 channel, I just find my fronts have plenty of bass on their own.

Concerning Tidal I don't think that would be cheaper than $3-5 for CDs, you have a monthly subscription or if they offer a life time. Or the cost if your purchase and download somewhere else. Either way. Like Oopwah said for CDs all you need is a computer which you already have, external drive,  Dbpoweramp software. The software once you have it setup which doesn't take long, its done. I literally put the CD in, click Rip/convert and 3-5 mins later its done and I am playing it.

At the end of the day though it is preference, do what you feel the most comfortable with. But don't be opposed to trying something different especially if there is a difference in quality for less or equal cost.

Will