I'll be upgrading to more efficient speakers sometime this year and I'm trying to narrow down my choices by looking at specs for one (there are other factors of course). I'm limited to bookshelves and since the couch is against rear the wall it'll be at least 14-15 ft away from the front speakers. I currently have 86db efficient speakers driven by a 70w/ch HK 525, however I do sometimes feel that the sound/speakers seem strained esp. when I have the volume turned up at -15 ~ -10db ref (my normal listening range). How much more efficient should the new speakers be? (will 88db speakers enought to eliminate the strain?). Is there a simple calculation to figure out the speaker's efficiency for a specific distance given the speaker's efficiency at 1wt @ 1meter? Does it even make sense to do that? BTW my room size is about 2500+ c.ft (family room) with 1 side wide open.