Not to make your decision more difficult, but have you seen the copper mods from Vapor Alley? I have been using a Q2V3 for a couple months, and it has quickly became my primary PV. It is reasonably priced, built like a tank, and, with different bats, will vape at 3.7, 5, 6, and 7.4 volts(Boba's Bounty at 6v, on a dual-coil carto, is my current "sweet spot".). Also, Super T will be releasing the P+ 18650 soon--a top shelf, american-made mod that will handle the same voltage combos(I think).
I like the all-brass copper, though, because every ding and bit of patina adds character to the mod, and I wanted a reasonably-priced mod that would stand up to an unreasonable amount of abuse.
Of course, if you feel like going big or going home, there is a very low number GGTS semi-buried in the classifieds.