Yeah, the Subal housing is quite expensive, its basically the top notch. I usually recommend Sea & Sea, however I spoke with our rep recently and they have chosen not to (Sea & Sea Japan) produce a 20D housing. This is very unfortunate.
The Ikelite housing is not a bad housing. Its a nice way to take your DSLR underwater. The controls are a bit tricky at first until you get the hang of them. You really need to watch the alignment of the control knobs and the buttons on the camera itself. I will be getting a 20D housing in from Ikelite shortly for demo.
If you are looking for a reasonably priced housing, then Ikelite is your best choice. Send me a PM and I will give you some more info if youd like as far as pricing, etc.
If you are buying a 20D kit, I would look at getting the 17-85 lens kit with the body. its a much better lens than the 18-55. However depending on what you are going to be shooting, you may decide to buy the body only, and get the lenses appropriate for your shooting purposes.
Any q's, just let me know.
Good luck, Mike