I don't think you need the Dome Port for Canon 17-85mm EF lens. I don't think you will want to shoot this lens underwater. Also its better if you can stay with one dome (8") and extensions. Do you have the lens for the Port Body for 8" Dome Port for Canon 16-35mm? You don't need it for the lenses you have listed. You definately want a good midrange zoom for topside use.
Some people like midrange zooms for sharks etc. but for me the basic 4 underwater lenses are 2 macro and 2-3 WA:
WA:
Something in the 12-24mm range. Canon's 10-22mm is stellar.
Sigma 15mm
Nikon 10.5mm If you shoot Canon there is no equivelent but you may want to look into the Tokina 10-17mm FE Zoom.
I'd stick with the Sigma 15mm and 10-22mm for now and see if Canon or others come out with a true FE. If you use the above lenses you won't need a diopter. This is good because diopters may introduce problens and prevent good over/under shots. Get the 8" dome port and extensions for these lenses.
Macro:
Canon 100mm USM macro is fantastic from all reports.
Canon or Sigma 50/60mm (get this lens first its the most useful and add the 100mm later)
Get the appropriate ports for these.
Lighting:
If you have the Ikelite housing you want to take advantage of TTL. So get the Ikelite DS 50, DS125 or DS200 1 or 2 strobes depending on your budget and travel preferences.
Ideally 2x DS200 would cover everything. But these are expensive and bulky.
2x DS125s are popular medium size. I have these and I like them. Everything I have fits in 1 approved carryon.
DS50s are good. But if you are getting 2 for cost, I'd recommend getting 1 DS125 instead and upgrading to 2.
Then you need either a single or dual sync cord and arms.
I would get ULCS arms 2x 8" bouyancy segments 3 clamps 1 IKT connector to connect to the handle and 1 Ikelite strobe ball connector for the strobe end (per side double this for 2 strobes) .
Get a good carron bag to carry it all in like a Lowepro roller bag or AW Trekker. Also get a large 12 pack size soft cooler to carry the whole setup on the boat.