Most RDA's nowadays have some pretty nice deck sizes/are pretty easy to build on. I started off on an Igo-L but very quickly moved to a dual-coil situation (Chimbus). I'd recommend skipping that jazz and going straight up to something like a
doge RDA. It's sort of an end-game RDA (ie: you won't need to get much else after it, as far as RDA's go), and the ability to remove the top bit instead of removing the whole top cap to drip is pretty fantastic.
Alternatives I'd recommend would be a Tobh Clone (the Infinite version is the best one for sure), or a Stillaire clone (not sure who makes the best one). Those feature AFC, removable top-bit (dunno what to call it) for easy dripping, and they all look pretty damn fresh.
My overbearing recommendation though, is the
doge. It ships at the end of the month, so now's a pretty good time to order (you won't have to wait a full 30 days), also the special edition Black and Copper versions are being sold right now. I'd recommend the black over the copper for sure, just because the copper is said to be super soft, and will scratch/blemish easily.
You definitely shoulda posted this thread in another sub-forum though, you're not gonna get many responses in this sub-forum.