I used to have a Nad amp from the late 80s. When it broke I changed to a Rega Brio which was a bit better. Still with my old speakers. I planned to upgrade my speakers but started to think about moving and did not know which speakers that would work. Then I found a great deal on a used Schiit Ragnarok 2 integrated and bought it. It was the best upgrade I have made! The sound improved a lot even with the old speakers. So you can get better sound by changing the amp, even with old speakers.
I do recommend the Ragnarok. You probably want the fully loaded version since it has both dac and riaa built-in. Just get a Raspberry Pi or another streamer and you’re covered.
[Edit]
The price is around $2k.