Yes, horns/tweeters are used on some bass amps to help drive the higher frequency notes. Personally, I think they sound like crap, but I am but one man and deeply partial to 2x15 cabinets. My opinion is subjective. Sometimes crossovers/biamps are used with tweeters, but bass cabs with them are usually wired so you just plug in the speaker cable and off you go.

Tube amps do sound better than solid states with basses, but we can get away with solid state amps more than guitars can. It's just the nature of lower frequency notes.