Thanks, everybody for the responses. Here are a few follow up questions.
1. From the specs, it looks like the SB105 and the Ikelite are closest in color temp (4700-4800), so from a color matching viewpoint adding a single Ikelite to the 105 would probably make more sense than a single Sea & Sea or Inon, which are in the 5400 - 5500 range. Do I assume correctly that matching will make my life easier in postproduction?
2. The recycle time and capability of the 105 do look like they could be limitations. From the specs (and experience) you can get between 40 and 60 shots on the 105 before recycle times start to wear on you. Fine for 36 exp film, but not great for digital I imagine. Recycle times are also longer, on average: 4-5 seconds v. 1 or 2 after a full dump. Moreover, if I start doing more manual work (as opposed to TTL) the 3 manual power settings on the 105 are likely to be fairly limiting, when compared to the dozen plus on the others. Does that all sound right?
3. The Inon recommendation sounds like I ought to add that to my list. Frankly it does look like a contender and is in the same price ballpark as the YS-110a and the DS-160. (a) Should I be concerned about Inon Japan's dispute with Inon America, which no longer distributes Inon in the US? (b) What is the difference between the Z-240, type 3 and type 4. Later model? What advantages?
4. Now: TTL. Other posts on this board indicate TTL is basically useless for wide and OK for macro but that you can do just as well manually with a little practice and trial and error. I have adjusted my thinking accordingly and have focused mainly on manual capability. My impression is that Ikelite does quite well with it's TTL converter (you need an Ikelite strobe of course), but that others are either crapshoots or twice as expensive and crapshoots. One combination I am considering, however, is dual Ikes with the converter. If anybody is using that combination, I'd like to hear how they like it. It's the one solution that might push me toward the single Ike bulkhead available in the Aquatica.
5. Also, the limited info I have on the Inon suggests that it has built-in TTL circuitry. Is this the same claim as everyone else makes -- yes, but you need a converter -- or is this a plug and play TTL solution? I'd be surprised if the answer is "no converter needed," but I can't get much info on this (since Inon America is shut down).
Again, my thanks to all for their help.