Piano and Trumpet can sound bright

If you're up for a speaker change, you could certainly change that quality in the sound. However, you'll change pretty much everything else too. I'd try replacing the silver streaks with something that's all copper - there are tons of options.

I played trombone in a ton of small groups and big bands - even large salsa bands. When a trumpet player wants to, he can burst your eardrum (although trombone can technically produce more volume, it's not as harsh). That being said, Miles can have a bright/brilliant tone, but it shouldn't hurt your ears if everything's right. The same should be said for piano. Even a guy like Michel Camilo who whacks the crap out of the keys doesn't sound harshly bright on his recordings.