Thanks for that Asbestos4004. I am gonna pick up an AGR+ and if I end up sticking with carto tanks, I'll look into some of the 'more advanced' options out there. I really like the Phiniacs and IBTanked tanks.
Phiniac's and IBTanked are definately my favorite carto tanks. Before you buy, I would like to point out what I see as the main differences between the two.
Phiniacs are thicker (at least the full size Phiniacs are, Skinny Phini's are a little thinner walled). They also REALLY grab onto the cartomiser after they sit for awhile. I never worry about the tank slipping off if I pick up my mod by the tank. It just isn't going to accidentally slip out. It really requires some effort to break that seal. The Delrin caps are not the most attractive, but are sturdy and functional.
IBTanked on the other hand are a bit thinner walled than the full size Phiniac, but thicker than the Skinny Phini. The caps on these tanks are much better looking IMO, especially if you get them color anodized to match your tank or drip tip. The tank is easier to unseat than a Phiniac which makes them easier to fill, but always leaves me a bit concerned when I pick up my mod by the tank. To be clear, these have never slipped completely off the carto, but have moved up to a quarter inch.
I truly love both my Phiniacs and my IBTanked, and neither brand has ever leaked on me in 6 months of use. The differences between the two might make one brand more attractive to you than another though.