UN is making both housings, their aluminum housing is priced at about $2600.00 and the Olympus PT-E05 housing should sell in the US around $900.00. Both should work with both E-520 and E-510 with little modification. I dived my PT-E03 housing below 150 ft. (45 meters) several times and I would expect to do the same with the PT-E05. Other than the cost difference trying to find a dealer for the UN branded housing is going to be a problem in the US.
Regarding the 9-18 zoom I am sure it will work well with the current 170 mm and 220 mm Olympus and Athena ports, but with a new extension port and zoom gear. Olympus entry level lenses have been excellent v. cost and this lens should be no exception. One of the thing I like about this lens is the ability to add a Magic Filter or other threaded type filters which can't be done with the 7 to 14 mm zoom.
A new more powerful strobe (Olympus UFL-2) is also being offered which will fire in TTL using fiber optics. It appears to be a new Sea & Sea design like the current Olympus UFL-1 which was later released in the Sea & Sea lineup of strobes.
As always you provide excellent and helpful answers, Phil!
After much thought and deliberation I decided to sell my E-3 and replace it with a double kit zoom E-520. I absolutely love the size, and the sensor should be almost the same (about a third of a stop less DR, though, but mostly the highlights - typically not a problem in Swedish water...).
If the Oly housing will go to 45m I think I will be better served by that one, cost to performance wise. I looked a little bit at the original Oly port for the 11-22... Is an 18 mm FF equiv too wide for a flat port? Just thinking about what port Olympus will recommend with the 9-18 lens?
I like the short single arm setup and might just end up with that as a starting point to just finally get a DSLR under water without having to give up on travel etc due to financial concerns. However, would like your input on the best double strobe setup. I'm thinking Athena, Inon or ULCS tray and handles with ULCS arms. I'm also thinking of starting out with the new UFL-2 rather than going for the far more expensive Inon strobes (although I would prefer them!).