Don't pinch the pennies. In the long run, it will be cheaper to have the camera and housing you really want. Even with pns cameras, you'll quickly be in the $1000+ range with strobes, accessories, etc. If you're worrying about a $75 difference between a 5mp and 8mp camera or a $150 difference between two housings, it will soon disappear in a sea of memory, lenses, strobes and arms, etc.
Just admit that you're going to spend way more than you want to, but realize that you're going to have this thing for years and most of your spare time will now be spent playing with little pictures on a computer screen. If you love your Sony and it takes great pictures, get the housing. You've used the camera, you know the settings and you can change things around quickly without thinking about it. Otherwise, pick the combo that really suits your needs. Housing size, viewer size and strength, focus time, raw or JPEG, memory type, battery type, hotshoe or slave......
The question isn't really what camera do I want, but what am I going to do with it and which camera will suit that use best?
Just admit that you're going to spend way more than you want to, but realize that you're going to have this thing for years and most of your spare time will now be spent playing with little pictures on a computer screen. If you love your Sony and it takes great pictures, get the housing. You've used the camera, you know the settings and you can change things around quickly without thinking about it. Otherwise, pick the combo that really suits your needs. Housing size, viewer size and strength, focus time, raw or JPEG, memory type, battery type, hotshoe or slave......
The question isn't really what camera do I want, but what am I going to do with it and which camera will suit that use best?