Rotel Questions

I am new to forum and didn't see a search function within the section to see if I could research before I post, so thought I would go ahead and pose a question.

Currently own a rotel RA-1520 with some B&W CM1's.

The rotel seems like it does a fine job. I have a iDac plugged in and sonos. Bought set up at hifi store in NC.

Thought the rotel was a good entry into the world of hifi stereo. But still yearning for a warmer/tube sound. Would love to have a Mcintosh set up one of these days.

Looking to do some upgrading. Questions:

1.) any recommendations/experience on tube based pre-amps paired with the rotel? And will it make that much of a difference?

2.) seems like the peachtree iDAC gets good reviews, any thoughts on the dedicated peachtree pre amps with the integrated DACs. Or do u still keep the dac separate?

3.) looking on rotel's website, looks like they also sell separates that would complement the 1520. Dedicated pre amp and DAC. Anyone have experience with these products?

4.) or should I just sell the rotel and upgrade to a different set up all together? I don't want to build upon something that isn't worth building upon.

Most of my music listening is enjoyed via sonos. Thoughts appreciated.
Rotel customer service responded to a similar email request. Must say they are phenomenal. Always prompt and solid. Perhaps this might help someone else in similar situation.

Basically told me that the RA-1520 not a product to run with separates. Or at least separating the product with a pre amp would make much sense.

What that said, any thoughts on DAC upgrades to help with sonos. Feel like the dac-it I have could be improved upon? Perhaps that could improve the system?

Thanks for thoughts. New to forum and appreciate advice.
I have used a tube pre amp with a Rotel class D power amplifier (RB 1572) and it sounded very good. No, the 1520 can't be used as a power amplifier as there's no main in input. When you switch to a tube pre amp you probably will lose a lot of features that you will find on your Rotel integrated, like tone controls. A good tube pre amp is pretty expensive too and then you have to get a power amp with that. If you still want to go the tube route, maybe you should try an integrated tube amp for your speakers, like the Audio Research VSi55 that can be found used sometimes for a very good price and the sound should be better than the Rotel but I'm not sure as I haven't heard that specific amp. Audio Research should be pretty easy to resell if you don't like it which is a very good thing to have in mind. You could of course try a tube pre amp and a powerful solid state power amp like almost any Rotel, or borrow from a hifi store. Just to see if you like it better than your current integrated.