The good news is theres a lot out there that will be a big improvement, I like how your thinking, starting with a good amp IS the foundation of a great sounding system. Have you thought about a Integrated amp? This kills a lot of birds with one stone ( no IC cables, Pre amp is built right in as well as a Phono pre ,possibly) SO I would look at a few nice quality Integrated amps.
Also, you can skip all this equipment and go with a Nice pair of ACTIVE speakers that already come with Amps, DAC’s, Pre amp, all this is built in and you dont need anything but a source component like a turntable or digital music streamer. KEF makes some very reasonably priced Active speakers (LS50W) as well as many other manufactures.
Minimally if you just want to change your amp, I would look to the used market and find a ADCOM GFA 555/555-II and find a nice tube based pre amp to pair with it, the Adcom was designed by Nelson Pass from Pass labs and is a real sleeper in the audio world, Paired with a proper pre amp it is excellent sounding, and Powerful (200/300 wpc 8/4 ohm), these amps were known to be in many record stores back in the day and they never shut off , they ran 24/7 and worked like battle ships (even better). People that used them at home im sure never came close to that many hours thats why you can still run them without having to replace caps! even after all these years. Sure some of them need to be gone through, ADCOM is still in business.
https://www.usaudiomart.com/details/650297245-adcom-gfa-555mk-ii/
https://us.kef.com/products/ls50-wireless-2?variant=42122054795511
Matt M

