Another +1 for room treatment. I had to move my Sopra 2s and system to a smaller room a few years ago and I first noticed the lack of bass but I struggled with soundstage and overall balance as well. It was very frustrating but once I introduced some homemade room treatment everything started to fall in place. I originally used a PremaLuna Dialogue integrated with very good results but it did lack some oomf when turning up the volume. I'm now using a Roger's KWM-88 (yes, another tube amp) and it's really amazing to my ears and audio friend (of course your MMV).
I have had times when the treble is too hot but I've found that for me there is something else going on up stream. Cartridge isn't adjusted properly, breaking in a new set of tubes, etc. I also just installed a set of Gaia's to the Sopra 2s and that further improved everything top to bottom to my ears (but I don't think they would do anything for hot treble).
There are a lot of great speakers out there, many mentioned about. Regardless of what you choose, definitely consider room treatment and experiment with speaker placement. It does take some time and effort but you'll get the most out of your investment.
Good luck!!