Hi,
I really have doubts about the Olympus quality (images). I have a Tetra 3030 with oly 4000. I'm very happy withit except I got a Canon digital rebel and no comparision points at all. There is the dpreview.com site will help you to decide....check the samples.
I did some research and for my budget and opportunity got across a canon/aquatica setup. I will relly think for I have seen so far.....go with Nikon or Canon.
Old excellent systems
Nikon D100
Canon 300/350
New
Nikon D200
Canon 10/20/30D
Pro
well...it will be over my budget...
Nikon D1X
Canon Mark II
Of course now I'm married to Canon because of the lenses I own (50mm, 105, 10-20, 15-30, 18-55, 75-300)
I will just advice you about getting a housing which ports will work on newer versions ....Aquatica, subal, Sea&Sea seem to always keep the ports re-usables.
Just my 20c