Another vote here for the K100. I love it! It's built very well and feels solid. The bottom button is great for Genesis style RBA's, since you don't care which way the button is in relation to the wick, and it's very easy to lock for building your coil and impossible to fire with just a few twists (not even all the way). The button is also stiff enough it doesn't wobble a whole lot even with a heavy RBA like the AGA-T on it, but still very easy to press. The AGA-T fits great on it, it's just a hair wider than the top of the K100. I use it in shorty mode most of the time, and it's very stable, especially when locked.
Pics with K100, eVic, and Vamo in 18350 & 18650 mode with a couple AW's for comparison. The K100 has an AGA-T+ on it and both the eVic and Vamo have Vivi Novas.

And here's one showing the K100 in 18350 vs the Vamo in 18650.
