I tried to answer your question a few minutes ago, but I ended up rambling, and canceled the post.
What do you have for a battery? It sounds like an ego or spinner type? Anyway, one battery isn't enough, because if it goes south on you, you're going to be very unhappy. I would recommend something like an iStick, even if it isn't the most powerful one, to go along with whatever you are using now. Always have at least two devices, in case one stops working, or one needs charging when you are away from a power source. Most people would agree that three are better, so you have a backup for your backup. That will make you much happier than a sub ohm tank.
I do rebuild most of the time, but I normally build in the 1 - 1.2 ohm range. I also have a subtank, but I like the 1.2 ohm coils just as well as the .5 ohm coils. I plan on rebuilding it most of the time, but I am going to get a pack of the 1.2 ohm stock coils. They will work with my old MVP 2.0 and my Vamo 5, as well as my mechs and the newer regulated devices, and I get just as good a vape from them.
From what you are saying, I wouldn't worry about a sub ohm tank, because you probably wouldn't benefit from it that much, but you would benefit from a better regulated mod, so you can experiment with different wattages and voltages.