Putting together underwater setup

I am working on putting together an underwater setup for my canon eos 20d. I currently have the camera, 18-55mm lens, 50mm macro lens, and a 70-300mm lens. I am looking to add a 100mm macro lens and a 10-22mm (made for small sensor dslrs) to my lens collection. I like my 50mm macro but sometimes it is too hard to get that close, hence the 100mm macro. I am thinking about getting those lenses and then the ikelite housing with the flat port w/focus for the 100mm macro. Am I understanding correctly that with this port I can either choose before the dive to use auto or manual focusing but I cannot switch my mind while underwater? I was then thinking about getting the 8" dome port system with the 5510.22 port body which accommodates lenses up to 4.125". This is the port listed on ikelite's chart for the 10--22mm lens. The chart says that this particular lens does not need a diopter but it is recommended to put a +2 diopter on for enhanced corner sharpness. Do you think I need to get the diopter and if I do is this port large enough to fit the diopter? Also, are you able to change the zoom with this lens while underwater? Oh yeah and I was looking to get two of the ikelite DS-125 stobes with ikelites SA-100R release mount 1" ball socket system with ttl capabilites. Thanks in advance for anyones input/advice.

Michelle