I would suggest the W22s to go with the QS4s and the W100 for a center but you could run 3 W22s across the front or a W2 center, if the room allows for a vertically oriented center. Have you watched the video on how to install the W series?
video Any of the usual names, Onkyo, Denon, Yamaha, will work well for that room, so pick one in the price range with the feaures you want and buy it, maybe even look at the refurbished units to save even more. A tube amp should be no problem as the W series is still a sensitive speaker so it takes very little to get good volumes.
So far as the wires that is upto you, Axiom has some flat wire that should be great as their regular wire is a bargain considering how fine the strands are. If you want to crawl around in the attic to pull wires go for it.
