I have the same desire, to shoot good stills and also do some video. I own a D7000, but don't want to spend that kind of money on a housing, ports etc.
I come from having a few good P&S cameras with an inon D2000 strobe. Another factor for me is my wife. She likes to shoot some but doesn't want the bulk of a DSLR underwater.
I have recently purchased an olympus e-pl2 and housing. This whole solution is about $1200 for camera and housing.
I have not tested it yet underwater. For me, it's the right compromise of size, image quality and video ability.
A nice thing about video is the one touch button. you can instantly capture video while being in a still mode.
There is also the olympus XZ1 with housing or the canon S95.
With your level of dive experience, you may be better served by a smaller system to start.
And remember the strobe is usually more important than the camera.