Additionally with Lahaina you can purchase the 2 tank boat dive and add a specialty course for $39 they have peak bouyancy, deep diver, naturalist, and boat diver. It is a great way to expand your diving education for a resonable amount of cash. I was there in december and did 5 days of diving and 3 specialties and had a great time. If you take the courses it is kind of like your own DM (depending on how crowded it is).DiveMe:On Maui, you might check into Lahaina Divers. They are a good operator for someone who might want a little more support. They run bigger boats, but put a DM in the water for every 6 six divers. They also do a lot of training, so have quite a few newly certified divers or divers getting certified on their boats.
I highly recommend the Lanai and molokini charters. If you experience allows, dive the backwall at molokini, my last dive there we saw 3 huge manta rays and dolphins.
Lahaina is a well run operation with nice boats and a good staff.
On Kauai we dove with Sea Sport Divers, they were a good op with friendly staff and a nice dive boat. They have a DM/videographer on every dive, the video is available for purchase of course. While we dove with them they gave us free nitrox for all 12 of our dives. We were lucky with them there was a few dives when it was just us 2 and one other diver and they still went out. It was nice they didn't cancel the dives because they didn't meet their minimum diver count. If your going to use them for multiple days let them know you want to go to different sites otherwise you'll end up at Sheraton caves repeatedly.
If you want more info pm me..