I have made the same transition, but with a D90 (unhoused), D7000 and D7100 along the way. I started with an Ikelite housing but have used Nauticam housings for the last 30 months. My thoughts:
Ikelite housings are good value for money and do the job, but there are advantages to a modern aluminum housing that in my view justify the increased price if the budget will stretch:
- Far superior ergonomics in use
- Somewhat less bulky and heavy when handling and travelling
- Most come with the now more prevalent and reliable fiberoptic connections for triggering and TTL strobe control
- Most other housing manufacturers have improved port locking mechanisms than the less than reassuring Ike locking mechanism, especially when on the surface where so many floods happen
- Many other housing manufacturers have easier to use and therefore safer housing back catches
- The standard Ikelite viewfinder is in my view quite poor, but just how difficult it is to use may depend on your own eyesight. Other manufacturers make accessory magnifying viewfinders for which adapters are available for Ikelite.
At least one manufacturer (Nauticam) make an adapter to take Ikelite ports to make the upgrade pathway less financially painful.
The 60mm Micro is a great lens.
None of the other lenses you mention are truly wide angle under water on a DX sensor camera. They possibly come into the category of jack of all trades but master of none. The Tokina 10-17mm (fisheye) remains an excellent choice wide angle for image quality and some zoom flexibility as long as you don't mind the fisheye distortion (or straighten this up in post processing). It works well with a 100mm/4 inch mini-port which is another advantage for travelling.
VR is not very important at the wide-angle end of the range, especially when using strobes rather than available light. Even for macro, VR is not optimised for the sort of movement that happens underwater, and water mass/viscosity provides some mechanical dampening against the higher frequency shake for which VR is designed. However I do keep VR switched on for lenses which have it, for what it is worth.
The DS125's are first class and quite powerful strobes. However they are extremely bulky and heavy and this is compounded if you take spare proprietary battery packs and the equally bulky charger. They are not great for travel.
In addition, they only work with electrical trigger and Ike TTL. The former has a reputation for lower reliability and requires comparatively bulky electrical sync cords. The latter limits the flexibility of their use.
Inon and Sea and Sea make a range of modern strobes which are light in weight, use rechargeable AA batteries which require widely available compact fast chargers and which will trigger and provide TTL optically with a very wide range of housings and cameras.
Of all these things, I think it was using an accessory magnifying viewfinder that make the greatest difference in my upgrade path,
My two cents worth,
Enjoy the great D7100!