The iStick is a wise choice. It corrects the problems of the iStick 20w. It is a convenient size and looks nice. The 30w has been out long enough that people have experience with it. The iStick 50w is obviously new. It is uncharted territory. As yourself if you really need 50w.
I have a Kanger Subtank Nano. With the 1.2 ohm coil it is almost a killer for a mouth to lung vaper. If I am not mistaken the Aspire Atlantis is only available with a sub-ohm coil. If you are a lung hitter it might be ok for brief periods. Ask yourself if you want to do sub-ohm lung hits all day long.
I suggest you learn to walk before you run. There is a lot to learn about vaping. Use the Emow with the 30w iStick for a few months. You may want to consider a Kanger Aerotank as they work well with iStick products. Learn your vaping style, what works for you. Learn how to take care of coils and solve problems. Let the dust settle with the new, unknown sub-ohm tanks. Then, go in a direction that works best for you. Remember, some of the people on ECF are enthusiasts who go for the biggest, strongest, latest and greatest. This is not necessarily the best route for a person new to vaping.
Join us:
http://www.e-cigarette-forum.com/forum/variable-voltage-apv-discussion/601111-eleaf-istick.html
http://www.e-cigarette-forum.com/fo...40761-little-itty-bitty-mods-under-100-a.html
Happy Vaping!