The 30W eleaf Istick will fire the Atlantis with the 1.8Ω Triton coil (10-13W), or 0.5Ω Atlantis coil (20-30W). Many folks feel these coils are under rated and fire them 25% - 50% over their rated values. You may want to get the 510 drip-tip adapter for the Atlantis if you use the 1.8Ω Triton coil with it. It's probably the best match with the Atlantis for your MOD. The Nautilus series from aspire are highly rated, and would also be a good match for your MOD. I use a Kamry 30W V2 with mine.
I absolutely hate the sub tank mini. It's far too hot a vape for me.
I'd hold out a month or two before getting a higher powered MOD. Several manufacturers are getting ready to re-release their MODs, hopefully with the problems fixed. Your best sources for vaping supplies, although not the cheapest, are your local B&M's followed by the manufacturer. Many of the Internet websites offering cheap supplies will send you problematic, sub-standard, cloned equipment. Some websites are legitimate, but don't look for deep discounts from them. Ask here, and in the manufacturers forums before you buy through the 'net. Your local B&Ms can give you support for your new devices. Get to know them, and their return / warranty policies, before you buy. ALWAYS verify the authenticity of anything you buy on the manufacturer's website.