The question would be since you just bought the 20w Vamo why would you buy a 100w rather then simply buying some replacement coils? If you are buying the tank for sub ohming then you would be looking at the various high wattage APVs available.
Several mods will go down even as far as .3ohms where you can pick and choose which suits your needs. While Sigelei gets a good rep I found them to be priced higher then other similar mods.
It's your call there as to what you are looking for. The specs show you won't have any problem with the Nautilus the way it is since that will take coils as low as the 0.15 ohm seen in the specs. If you are strapped at the moment cash wise since once you get started there's always one more thing that will get you fired up! wait until the BF and holiday discounts are rolling and then browse what you can get for what price(s).
In now just a little over two years time after the first starter kits(holiday gifts included) I estimate I have cleared the $4,000US mark by close to $200 or so total. It can add up fast at times!
Last november during the first week when getting the MVP in for example I realized I had to get into some better tanks as well as moving up from variable voltage to VV/VW more progressively and found myself already outgrown three mod stands! Does that say anything? hhmmm... but weighed against the former $300-$400 on cartons to smoke is a much healthier investment with the $$$$ I won't be handing out to "Big T"(obacco)!
This year being well situated and the first variable wattage manual not automatic epipe will be out at the end of next week which should just about complete the collection here besides wanting a few more of the less costly batteries and likely a few other tanks. The first epipe I ended up and gave away last year was an automatic with plastic inserts and the next newer model I missed by one letter 601C instead of the DSE601 I got!
Fortunately I could pass that along to someone else now vaping rather then sticking with a recent smoking habit.