I have the aspire CF Sub Ohm and its a great battery, I actually have two of them, and thats the down side. If the battery dies you have to have a second one to use while the first is charging, thus why I ended up buying two of them. I would recommend if you are going to stick to aspire products to get the CF mod, its the same exact thing except you can swap the battery when one dies. The CF Sub Ohm has an internal battery. So again my recommendation would be to get the CF Mod.
Also I use the Atlantis as well its an awesome tank, out of curiosity why don't you try another mechanical mod? you get better hits, I'm using a stingray x with the atlantis and I LOVE it.