Yoke is the standard connection type you'll get at most LDS, then there's DIN, which a lot of pros swere by...tho o-ring is in the reg. not the tank.
The GT3 is fine reg and I'm a big fan of Oceanic and its sister company Aeris, my gear includes an Oceanic CDX-5 w/DVT 1st stage w/ Oceanic GT3 2nd stage , Slimline 2 Octo, Oceanic SWIV Navcon, Aeris Atmos XT BC (this is nice BDC 'cause its a hybrid between back inflanted & jacket)..any way I got it all through
www.divers-supply.com an Oceanic authorized dealer with great prices... my set up was less than $800 (might have been an extra $50-60 with a computer like in your set-up)...though it was a few months agos but you can call them up and get even better pricing than those on the website.
Also, as far as going with an Air2 there are many mixed feeling about it, keep reading on the board...and you'll get better info...concider an alpha 8 octo, but the slimline is good if your on a tight budget.
Ohhh...ad as far the the DVT goes, it something to consider, you'll also get mixed reviews on it all over the board but mine has it and Its really a nice extra safety to have after such a large investment....for only a few buck more.
Good luck and happy buying.