I love my 75w tc sigelei but man, I use my tugboat on it at about 50w and its battery life goes by pretty fast. Probably like 3 to 4 hours. But it looks damn good and it's reasonably small.
If your always going to use an rda I'd probably go with the sigelei 150w tc instead. I like the finish on it but I'm not a fan of the little ramp up to the 510 base, but with dual 18650 it's battery life will get you through a whole day.
If I were you i'd probably get the sigelei 150w tc and some 4 Samsung 25r's from illumn. This way you can have 2 getting charged or waiting, and you can have 2 your using in your mod untill they are at about 1/3 charge, then you can switch them out. You will have to marry those batteries when you put them in your mod.