Ive used the Theatre 4 for HT with both the Delta and the JBL 2226.And I've heard the 7Pi. It's all about trade-offs and compromises. You really need a SUB-woofer whichever system you use to get those 15 and 20 Hz spaceships and explosions. That aside, the greater detail and tonal quality of the JBL 2226 screams do the 4 Pro or the Pro 7. Even tho' the Delta goes lower, it doesn't go to 15 Hz. Then there's budget. The JBL's are dear, but you will never regret using 2Pi's for surrounds, eliminating the center (which you don't need anyway) and spending the money upfront. Got the bucks?, 4 Theatre Pros or Pro 7's with a waaaay low sub.