Yes on the chrome/steel - get an Aerotank for the better materials I reckon - the plating does wear off after a bit of use with the plated chrome gear - they go kind of yellow and manky-looking.
You can also recoil/rewick the Kanger heads quite easily, even though there is no RBA available for those tanks, which is good - saves tons of cash as well as providing a better, more tailored vaping experience.
All those tanks are pretty old by now - I mean they still *work*, but there have been *some* real advancements in MTL vaping in the intervening years.
I personally wouldn't spend that much on a Nautilus these days - I really would look towards getting a newer tank at that kind of price (you can get a really decent Kayfun v3+ clone for USD$12), but the Kangers are cheap enough.
It really isn't hard at all to rewick/recoil RBAs on tanks with nice decks on them - you can even buy bags of 50-100 pre-coiled coils if you really can't be bothered wrapping them.
Rebuilding the Kanger heads can be a little more fiddly, as they were designed to be disposable, but once you've done a couple a few times, it really does become second nature - most of the time you're keeping the coil, and just replacing the cotton wick with a fresh one.
EDIT: As for your other threaded tanks, you can get an eGo-510 adapter to use them on 510 mods, or vice-versa. They're good as you can keep them in all the time and use them with both kinds of tanks, and they act as a 'thread saver', saving the often soft connector threads from stripping and wear which can be a problem especially on some VAMO models.
