Well it's a matter of really how far you want to go. If you want a great right out of the box mod I would say to go for a sigelei 100w plus. 100 watts is all you will EVER need even in the future with rebuilds AND it's only $100. Before you get into those I would seriously recommend reading up on your battery safety and ohms law but that's a different story for a different time. It will be all the performance you need and then some for the Atlantis.
Remember, we don't know if/ how bad high wattage vaping is on our lungs yet. If you want something that's all about safety I would say to go with a dna40 device (just wait a little while longer for the kinks to all get worked out). However, if you really get into rebuilding and "cloud chasing" you will likely want to have more watts. 40 watts is great and all but it will limit quite a few of the builds that you will be able to create. Some builds just only reach their full potential at 50+. Although 40 will be enough to unlock the potential of the Atlantis. Reason I am not recommending dna30 is simply that there really isn't a point in buying one when for a marginal amount more you can get a dna40 which will be worth the extra cash.
It's a matter of choice. For me the choice was easy, I went from dna30 to a sigelei 100+. As much as I liked the new temperature control features, I am simply at a point where some of the builds I am making really only reach their potential past what 40w can supply. If evolv makes a dna80 with temp control ill be right back on board though.