Hi Greedo, I use the 6'' dome with the Tokina 10-17mm on my Aquatica with splendid result, why I choose this one, when I obliviously have choice working for the company (see signature) is for its size (and in your case, price), plus it will work fine with the 18-55mm, I would recommend the larger 8'' also as a more flexible solution if you want frequent use of larger rectilinear wide angle lenses and the even larger glass dome 9.25'' dome if A) you want to contribute to my retirement plan ;-) and more seriously B) if you plan on using wider rectilinear wide angle lenses such as the 10-22mm and plan on doing a whole lot of over/under shots.
The 100mm macro is the best choice you can make given the info you gave us no matter what housing you choose, I would consider adding a 1.4x tele converter from Kenko for using with both the Tokina 10-17mm for extreme close up wide angle and the 100mm for those little rascals, plus the extension required for the 100 macro can be used with the Tokina+1.4x converter and the one for the 10-17mm & 18-55 can be added to the 100mm one if you use the 1.4x and the 100mmm together, this will make for a package with maximum punch with minimal luggage footprint.
As for strobe connection: the housing can also set up with both type of connectors Optical and Nikonos type (or optionally with Ikelite, or S6 for that matter, if it flashes we can connect it!) and we also officially introduced the 20065-HYB version which has both optical and Nikonos type installed when shipping (we did quite a few 7D housing this way from the get go, but did not have an official item number for it. But stick to your choice its A+ and the one I am getting for my own kit.
Now for the Viewfinder, I wish the Nauticam pundits would get their facts straight. they are not the only one with user adjustable dioptric, we do and its a simple affair that you do only once with the mechanism safely inside the housing where it should be, that is unless you plan on sharing your housing with multiple visually challenged underwater photographers, in this case you could adapt their viewfinder to our housing, if you don't mind having part of your rear LCD blocked off by the overhang of their design. (sorry, but misinformed statement, innuendo and half truth irritate the hell out of me).
here is a list of the items you should get quoted on should you consider an Aquatica.
20065-OPT housing for 7D
FOR WIDE
18409 6'' dome port
18484 6'' dome shade FE
OR
18405 8'' dome port
18480 8: dome shade FE
and
18456 Extension for both the Tokina 10-17mm & Canon 18-55mm
18717 Zoom gear for Tokina 10-17mm
18703 Zoom gear for Canon 18-55mm
FOR MACRO (2 choices)
18453 Extension for Canon 100mm Macro (required for both choices)
and
18428 AF Flat Macro port
Or
18426 AF/MF flat Macro port
18700.1 Focus gear for Canon 100mm Macro (both new and old version)
There is also a kit including the Aqua View (20065-OPT-VF), but the supplied standard finder let you see the integrity of the camera viewfinder image quite well, the Aqua View (and other extended viewfinder alike) basically improve on that by enhancing what you where seeing, making it both larger and easier to see, as I tell people, its the kind of accessory that does nothing to actually improve the quality of the final images, its expensive and quite unnecessary until the day you try one, then I double dare you to want to remove it from your housing. its like a big screen television, it does not make the picture any better, the actors are as genial or lames, but it make looking at the movie that much nicer.
Lastly I suggest you go in a shop preferably one that carries both makes and more, (The Hugyphot is also a nice rig if they have Optical connectors available). then you are less likely to get biased information, admittedly as a member of the industry I am biased toward my own brand and very conscious of that fact, it is difficult sometime to remain informative and credible, I just keep reminding myself that I got in this business because I was an underwater photographer, and that is how I joined this forum, as a underwater photographer willing to learn and share and eventually improve my skills both as a maker of images and of the equipment used for making them.