I'm driving Sopra no2 with a Hegel H30A. I really like this pairing and don't have any brightness. That amp might be too much cowbell but I would take a look at the smaller Hegel H20, should be plenty of power and better form factor for you. I know firsthand that Hegel has a deep demo fleet so maybe you can get a loaner for a local dealer.
FWIW I have found that my Sopras are sensitive to rake. If you have only tried toe in/out I would recommend experimenting with the rake angle (front/back tilt). Good luck and cheers.

