On the mechanical front, I have the Kamry K100 and I love it. Mod-wise, I think the differences are overplayed, honestly... at the end of the day, it's a battery tube. People get all hot and bothered by voltage drop, etc... I generally don't obsess about it.
I am a huge fan of my Sigelei #8 with an RSST - I just got a Fusions SG-1 Hybrid Kit for it, but I haven't slapped it on yet. The RSST is nice for a Genesis Style Atomizer - mesh seemed to be easy enough to get used to as a wicking material. It does have a longer break in time for me (2-3 tanks) before it loses the metallic taste. I am still on the same wick I rolled 2 months ago, though...
I have an Octopus and it's my favorite dripper, but it takes some modding... plug the stock air holes with toothpicks and drill a 2mm hole in the side of the cap. All things being equal it's been a royal pain the rear, leaked more liquid that it's vaporized, but I learned a ton in the process and it's still my favorite full size RDA (due in part to the fact that it has thumb screws and no allen wrench is needed). The smaller version (Bully, or Squid) is nice for testing liquid.
I am a recent Igo-L convert, due in part to Hawk and gotalot. Gotalot traded me one for some juice and I really like it. I still haven't rolled a coil on it yet, using his microcoil on cotton at first... then fished some Ekowool through the same coil. He drilled it out, not sure how big the hole is. I have a couple more coming just for play.
Finally - if you can find any local, support a local vape shop. Fasttech, VaporBreak, etc will save you a bunch of $$$, but you're pretty much on your own from a service perspective. At the end of the day, it's not like there's a ton of moving parts in a mechanical mod or an RDA, so I confess, I went the cheap route despite the slow shipping - that, and there's no one local who carries the mods and RDAs I wanted.