I would highly recommend a center channel for movies. it will take quite a bit off the amp load (which seems backwards but actually isn't) and increase relative volume levels ~+3 db while actually offloading amp duty quite a bit.. at probably ~20 watts total your system would run ~90db. 90db is loud in my opinion, which is above the level of when hearing damage sets in- so i'd keep that in mind.
now if you want reference level action, you will have to integrate a power amp, or 2, and a sub, or 2. there's no way around that unless you plan on getting super efficient speakers made specifically for cinema or live stage (think klipsch, jbl, qsc... all of which are designed to be paired with amps and subs.)
personally I'd start with a center channel, movies change quite a bit for the better with a center channel working. next would be a sub that does 25 hz reasonably (many do). then I'd consider a power amp, in my opinion any amp will do for movies, as long as it's quality construction and is quiet (fans to cool it.)
good luck on the setup, i'm jealous of your nrt's!