I dont think gates make still camera housings anymore. Your options are Ikelite, Light and Motion, Fantasea and then the camera manufacturers (Olympus, Nikon, Fuji etc) make their own. I think the Ikelite ones are more robust, and the Light and Motion ones are great, but expensive.
Try to find a digicam that has minimal shutter lag, good optics and shoots raw if possible (but dont bother about Raw if you're not keen on computers). There is a thread on that here, and lots more like it on the digicam forum.
Olympus and Canon seem to be the favourite ones to house underwater. If you go for one of the manufacturers own housings i would suggest Inon strobes, if you go for an Ikelite then i'd go for an Ikelite strobe.
If i was going to buy a digital camera soon then i'd be looking at an Olympus, probably the SP350, and i'd probably look into the ikelite housing as i already have ikelite strobes.
Half the fun in underwater photography is shopping for all the crap that you 'need' so take your time and see if anyone at your local diveshop has something you can hold in your hands. Also, there may well be some new cameras released over the summer, so if you don't find something that you fall in love with using it on land, wait a while.
If you don't like the menu system and usability on land you'll hate it underwater, so definitely go and bug the folks at your camera store and test lots of cameras.