The standard choice for Baritone Guitar is a Fender Twin. I guess a Fender Bassman would be pretty good too. Both of those are big amps with several speakers though.

It sounds like a jazz-type solid-state amp such as the Polytone Brute or Sessionette 75 would suit you. I would go for a 12" speaker definately though - its doesn't have to mean boomy, and 10"ers just aren't up to the job that low down.

Try a Brute and see what you think.