I'd look in to the new Sigelei 20W (at
FastTech for $84). It just received a glowing review from Phil Busardo for it's performance and build qualities. He mentions a few negatives, but nothing that should discount it from consideration. Overall he says it's definitely on par with DNA20 MODS. It's adjustable from 7-20W in .1w increments, fits both 510 and eGo tanks, can do sub-ohm down to .65 (according to Busard, though the literature says it'll go down to .5), and has readings for Ω, W, V, and battery charge. It can only use 18650 batteries.
There are a few features listed on the site that Busardo either missed or they are not there like a 5-20 second cutoff (this appears to mean that the fire time it is somehow adjustable, but Busardo said his is at 10 seconds and said others may wish to make it higher). I also didn't notice a puff counter or "settled vaping time" (whatever that means) during his review.
Since it's new one obviously can't make any claims as to its long term durability, but Busardo says it's built like a tank.
If not this I'd look at a DNA 20 or 30 device like the Opus D or the really cool NES controller MOD. The regulated MODs that are NOT PWM based will give a very smooth vape.
A Mech MOD with a Kick or Kick2 might also fit your needs, though it isn't nearly as easy to adjust a a true VV/VW MOD, but it will make your options virtually unlimited and still allow you to control the wattage.