I just bought an Elmo HP-L3550H Overhead Projector. It can take three types of bulbs. ENX-5, ENX, and FXL. The lumen output is 2900, 3000, and 4000 respectively. It doesn't come with any bulbs. What would be the best type to get, and the best place to get them? The ENX-5 is supposed to have a longer life than the others, but I don't know how much longer. I think they all cost around the same, but I only looked in a few places.