For a boat dive, I would highly recomend Extended Horizons. We dove the Monolith & 1st cathedral with them, I couldn't imagine how the trip could have been improved upon. Its not a cattle boat, they offer larger tanks, and you dive your own air.
For guided shore dives, Shaka Doug is pretty hard to beat. We dove 5 graves with him and the trip was excellent. We were staying in Kaanapali, and it was well worth the drive down & back to dive with Doug.
The one "can't miss" dive you have got to do is Mala wharf. It is a great site for a multitude of critters, and your best bet to get up close & personal with white tip reef sharks. The entry from shore is a little difficult, but well worth it.