Get 804's for years (not larger footprint) and get good Velodyne,Martin Logan (very fast-I like them ,Vandersteen's
REL,more than large slow subs-all use multipil faster drivers) without going nuts because of how much rear low level content.You's save bucks and have more crunch asJet swooshes by.Wish you had mentioned electornics that are mated.Bryston epscially used ST series with long warranty are great value.Maybe use one of their two way+sub x-overs in back.But now with 7.1 sets ups etc you could feed center rear into sub instead of full range speaker Though if you wanted you could easily order single 805/804).
Chazz