I went with Buckeye Hydro (he posts here a lot).
I got a Chloramine Special RODI system. Local utility treats with Chloramine, while the water is good it's VERY inconsistent. They swap between river, lake and ground water all the time with no real notice. At homebrew scales, its far more economical to do RO and add salts I need than try to run a same day water analysis on whatever HRSD decided to put in the mains this week.
http://www.buckeyehydro.com/chloramine-special-rodi/
I went with 50gpd, as it was a reasonable capacity to have that can fill my HLT overnight. DI is just an add on that I'm using since I do a little lab work in my garage so it keeps me from having to buy distilled.