Large MP3 Library from 2000s CD conversion/rip/sunset

I have a HD filled with iTunes from back in the day.  I plugged it into the usb input of my Cambridge Audio streamer and the files all appeared in a separate library in the streamer app and played 

My MP3 story.

Nephew wanted my advice for a new receiver for his new apt.

I made him understand, it would be the 1st of many 'stereos' in his life, so stay in budget, any decent brand, proper pairing with his existing speakers.

I found one on sale, in town, next door to the Audio store with expensive stuff, but also some good used stuff. Let's have lunch, check them out.

The sale was on, they had them, but not set up to listen to. I said, get one out of the box, get it ready, we will be back after lunch.

We looked at the impressive vintage stuff, still over budget, had lunch.

Back to listen, oh boy, it sounded like crap, my nephew looked at me like I was full of crap, I said something to the sales kid, he said, "I know, I told him MP3s sound like crap" pointing to another employee. 

It was Rusted Root. I said, wait, I have a RR CD in my car, got it, it sounded awesome! Nephew bought the thingy.

You had a 2 TB drive, you said? 4000 CDs ripped lossless into wav or flac is 2.8 TB or so.

So, why did you rip it all as mp3 dude? You couldn't get one more drive? What's the matter with you?

Anyways...A amp like the Yamaha R-N2000A... if you can get your hands on one offers one of their proprietary features to enhance/salvage mp3s. It sounds good....to varying levels of success depending on how lousy of a mp3 rip it was.

Another brand  has tried to offer similar features and it sounded botched a lot.

Who knows with the AI tools these days...you may be able to find some other smart tool.

Advice on utilizing and accessing a 2TB storage Drive filled with MP3s that were ripped from early 2000s when I 'left' the CD world and sold approx 4000 CDs? Purchased an Eversolo for streaming thinking it would help with this library but haven't got it all hooked and integrated yet. Advice on best software to use as well? Any options that upgrade MP3 format? Some were ripped at higher bit rate, some? not.