Well, as I sort of alluded to I use the 1801's mostly for home theater duty (yes, I know, that's like giving the dog a fine filet mignon... but I like high quality for everything I do).
I don't generally find it necessary to play them that loud for music, and for HT I probably end up with the volume around 80-85 average with a group (or whatever the volume is where you have to shout at the guy sitting next to you while the action is going on), it's those huge transient spikes of power and volume that concern me. I guess from the responses though, throwing 250+ watts at it for a moment while someone gets eaten by the bad guy isn't going to make them lose their magic smoke.
I haven't really noticed any problem playing them with any amp I have for normal music listening though, no efficiency problems here. As my main theater grows in size however (now 25'x40'!), I am finding the need to push more and more watts through whatever speakers of the day I am using, to get the volume up to appropriate levels, hence the need for big amps.
I haven't beaten on my 1801's in this way yet, but I want to swap them into the big theater system for a bit while I work on the next few upgrades. Next up is a pair of sealed Avalanche 18s, in some rather largish boxes. That ought to tighten up the low end pretty good over the old 15" Tempest I was using. Do you think I take this stuff too seriously?
