I realize you said you didn't really want a clearo because you wanted it to be fairly unnoticeable, but with an 808 device you might want to consider a smoke colored mini tank from SI or halo. It's a kanger t4 knockoff and speaking as a owner of a handful of t4s I love them. They're roughly a mm wider then the cartos but they're so much more user friendly
The T4/mini-tank is the clearo I've been using and I think it's very good. My only issues with them (besides having to tilt them to wet the wicks, but that becomes second nature quickly) is occasional "spitting" or getting a drop of juice/condensation in the mouth. Certain juices (e.g., Halo's Voodoo) seem to gum them up quickly but at least they're easy to clean. No leaking issues so far but I am concerned about the possibility of the press-fit mouthpiece popping off while I'm carrying it in my bag or my pocket. I've got some e-Smart clearos on order to try next. They appear similar to the T4 but hold a little more juice, MAY have longer wicks (depending on which picture is correct) and have a screw-in mouthpiece. I'd also like to try the M3 clearo.
As for carto tanks, I don't picture myself using them as long as I'm in 808-land but I won't rule them out for the future. As for REOs, VMods, etc. I really dig the concept but not the appearance or the price (I'm not cheap by nature, just on a tight budget out of necessity).