Just dropped in on that one, I don't cruise the strobe section a lot, 
Let me shed some light (pun intended) on this.
Your Aquatica D700 comes with an internal switchboard that allows you to go from 2 pins on each bulkhead for full manual to 5 pins / 2 pins for use with a TTL converter (or a housed Nikon iTTL flash). Given your current choice of the Sea & Sea YS 110 I would go with the Sea and Sea converter (the latest version), all you have to do is move all the small switch to the up position and plug the converter into the main connector (the one with 5 pins activated).
If you do plan on using your Ikelite Strobes you should first check with their website compatibillity chart to see if your strobes are compatible with the iTTL converter. See http://ikelite.com/web_two/ittl_adapter.html at the bottom of the page there is a link for serial number compatibillity.
if they do, then you will want to get the 4302 iTTL converter which is compatible with Nikonos type connector which are 5 pins (we have) and depending if you want single strobe then one cord 4103.51 or for dual strobes uses cord 4103.52, it work very nicely (that what I personnaly use for lighting).
Now before you ask why there is only one connector that is 5 pins while the other is 2 pins, Nikon will not tolerate two hardwired flashes connected to the camera (nothing to do with the housing) so let say you had a pair of SB800 that you wanted to put in housing and bring underwater, you would only be allowed to connect one SB800 to the camera/housing, the other would have to be triggered optically, just like using it top side. putting 5 pins / 5 pins on a housing is seriously asking for trouble as if you where to connect two strobes or flashes (BTW can anybody explain to me why they are called flashes up there and strobes down there????) you would freeze the camera solid. 2 pins / 2 pins is different since only the sync and ground are active.
The TTL converter kind of tricks the camera into thinking its dealing with a single dual head strobe, that makes it kosher for the camera 