I think there are two main reasons for the perceived brightness. Reason number one is speaker set-up. 95% of audio enthusiasts don't take the time to learn proper speaker set-up and methodically find the sweet spot. Read Jim Smith's book Get Better Sound for the methodology. And some don't even try in order to appease the wife.
The second reason is the Rotel digital amp. Class D is getting better and better but a five year old Rotel design is not a good match for the Monitor speaker which will expose every bad tendency of the Rotel. You need a warmer sounding A/B solid state amp. In your price range, I hesitate to recommend a tube amp unless you can find a deal on a used PrimaLuna or Pathos or Manley or similar.
The second reason is the Rotel digital amp. Class D is getting better and better but a five year old Rotel design is not a good match for the Monitor speaker which will expose every bad tendency of the Rotel. You need a warmer sounding A/B solid state amp. In your price range, I hesitate to recommend a tube amp unless you can find a deal on a used PrimaLuna or Pathos or Manley or similar.