Definitely a Dual Rec, I've never heard or played a Single I liked, and the Triple just needs to be cranked louder to sound good. As for 2 vs. 3 channels, I'm gonna go against the grain a bit and recommend the 3 channel models, every 2 channel clip I've heard (through V30s anyway), not to mention the countless ones I made while I had one, just had an abundance of fizz around 6k that I could not get rid of (moving the mic from the dustcap took away bite/clarity; turning and the treble/presence knobs focused mainly around 3k/4k, respectively; and turning down the gain made it sound, well, undergained). Check out these thread for more info:
http://www.ultimatemetal.com/forum/rate-my-mix-tone-threads/522517-guess-amp-no-ts.html
http://www.ultimatemetal.com/forum/rate-my-mix-tone-threads/499363-bit-dokken-c-rectifier-d-2.html
http://www.ultimatemetal.com/forum/...2-ch-dual-rec-new-interface-better-tonez.html
And here's a quick clip of the best tone I've gotten out of mine through my Recto cab (from my upcoming EP),
with EQ (narrow cuts at 700 Hz, 2k, and 6k, ranging from 1-3 dB, as well as HP/LP and Multiband comp on the palm mutes) and
without (just HP/LP and Multiband comp). And while I haven't recorded a 3 channel, I know all the fizzless Rectifier clips and album tones I've heard have been with 3 channel models! For reference, I'd say 2 channel = This Godless Endeavor, 3 channel = Behemoth's Demigod, take your pic
(actually though, if you can afford it, I'm pretty certain the Roadster is my favorite of the bunch, slightly darker than the standard Dual Rec but so beefy, I want badly
)