You seem tio like Casio’s and probably know how they work. Unless you want to change brands I would pick a Casio that can be housed in your price range but is a definate step up from what you already have.

The EX z6000 looks like a nice choice. If you get one that works.

For other ideas check out:
http://www.digideep.com/forum/viewtopic.php?t=2004&language=en
http://www.digideep.com/forum/viewtopic.php?t=2002&language=en
http://www.digideep.com/forum/viewtopic.php?t=1966&language=en
http://www.digideep.com/forum/viewtopic.php?t=1971&language=en
http://www.digideep.com/forum/viewtopic.php?t=1986&language=en

hope that helps.
I also replied to your strobe post to get you started there.

Giles

I prefer result from Olympus and or Canon for underwater results.
Olympus is more consistent but both tend to give better results underwater.

Housing wise no difference as they all make their own housings, which probably come from the same japanese factory.

without going SLR I would pick the

Canon S70 as the cheaper option ($350). Very good specs, quick, good low light (not the best but good) and has RAW so you can do post processing for tougher shots.
or
if youj can find one Olympus 7070

Others to think about are the Canon A95
or expensive
Nikon 8800

Although if you spend over $500 you may as well go for an entry level dSLR.

big LCD’s are nice, but common on the v small compacts now.

Good for underwater but the camera’s are not necessarily.

wisely spoken giles! We have also some reviews online from different
users to give you a better impression on what to look at / compare:

Sea & Sea DX-D200 housing review by JP Trenque
http://www.digideep.com/english/info/html/1251/

and

HUGYFOT D200 Housing Review by David Barrio
http://www.digideep.com/english/info/html/1250/

That is correct.

It says it is optical quality so I doubt it will be too bad but not perfect no.

But you wanted cheaper, and that myfriend is cheaper, Housings for cameras do not come cheap. And the WA Marine Bags may seem simple but they are more expensive for a reason, as then are the molded housings .. If I were you I would look at getting a PT housing for the 5050 the plastic housings made by Olympus .. it maybe more money but well worth it, even if you are not going diving it will be better protection and better quality.
Giles