Boas are a great choice..More active than BPs (and IMO, better to handle) but not hyper. If you want something that will be even more active, similar to a retic, you could look into carpet pythons. They are much more active when handled, climb and perch...Make good display snakes, but also leaner / thinner than boas. Some localities can get 7-9' most stay a little smaller. I have a jungle jag and he is a great snake too, but was a lot more defensive / nippy as a baby... Also, if interested in them, I'd avoid a jag, as they have neuro issues similar to spider BPs which can make handling more tricky (he is prone to falling). Jungles are smaller carpets, have great colors, and are very active. They are not heavier-bodied like a boa though, so if you want weight, a boa may be a better option. My male carpet is about the size of an adult corn snake in terms of width right now, but with about 6' of length.
If you want more info on boas, check out the websites of legacy reptiles (good for pics) and Cutting Edge Herp (good for pics and information on size, etc.). Vin Russo also wrote an excellent book, the complete boa constrictor, which I highly recommend.