I own a pair of Belles with refreshed AA crossovers (Crites kits). They are incredible at low input levels.....I have driven my Belles with a 5 watt Chinese tube amp....So, having said that, there are a bunch of questions to be asked...
XX- Before getting to the list below...are you sure all of the drivers are working properly, and the speaker wiring is correct?
1. What are your listening space dimensions and properties? (Carpet, flooring, furniture, wall construction, ceiling construction, any acoustic treatment)
2. Where do you have the Belles situated in reference to the rear walls, side walls?
3. What are your listening parameters? (How far apart are the Belles, how far are you from the speakers?)
4. What kind of music are you testing them with?
5. Using any kind of room correction?
6. Are they properly configured through your processor? (small, large, etc?) Have you tried test tones through them?
Probably lots more questions to come, but this might be a good start to help you.