For some reason none of the others have said this...the IGO-M, especially the version 2. it has huge airflow, a large chamber, and helio style post system. I have all the rda's mentioned and they are all good, but stock out of the box, the igo m out performs them all. The only problem with the igo m is the post holes will only get you to 22 gauge, twisted 24g is a real hard one to jam in there. It can be drilled out, but I can out perform most crazy twisted or paralell builds with my igo m by wrapping 24g micro's. The other rda's mentioned are great also, but for the money and ease of use the igo is very underrated.