I ordered a MakerBot Replicator 2 yesterday after visiting the previously mentioned 3D printer show at the Javits Center. The show was a bit of a disappointment -small with not many vendors- but a success in that in confirmed my belief that the replicator is the best option for prototyping the building toy hub.
A few more tools have arrived. The tap and die set will work nicely to put threads inside the plastic tubes, and the digital calipers will help greatly with fine measurements. I should be able to move into rapid prototyping as soon as the printer arrives!