Speaker Effeciency and Bass Production

Thanks much for the responses! It is interesting to note that so far I have used 3 different sets of tube amps so far on this setup with no as yet noticeable problems (although I've yet to push it VERY hard):

AES Sixpac: 50W push-pull triode
ASL Wave 20: 20W push-pull
Wright Sound: 10W push-pull triode

I do wonder if there is a formula than can calculate increase in efficiency based on low frequency cutoff. In other words if an amp can drive speakers full range to 94db in a room just before a certain clipping distortion, then if the amps are high-pass fed the same signal at a certain frequency (lets say 80Hz), then what SPL can the same speakers in the same room be driven to the same clipping distortion?

Onhwy, thanks for the link to the chart. According to that chart, I would need approximately 30W or so at peak levels; although isn't calculating efficiency a little more complicated as Bob_reynolds suggests above?

Onhwy, I don't know specifically yet which amps I'm considering, but thinking about some type of SET or OTL amp. Both can be attained with fairly high amounts of power, but I don't want the complexity or power consumption of anything above say 50 watts or so. A couple of amps I noticed were ASL Explorer 805 and Atma-sphere S-30 (I am concerned about the Atma-sphere's ability to drive my speakers due to impedance).

"So the system could sound cleaner, less distortion, but it won't go any louder."

Yes, the question is how much more *clean* non clipping volume can be had by not pushing the main power amps to provide low frequencies?

Cyclonicman, what are the amps that are powering the main speakers, and is it enough power?

Thanks Racamuti. I believe the crossovers in the main speakers (Opera Quinta) are relatively simple, and I am doing the crossover between the subs and main speakers in the digital domain (using a Tact 2.2XP). I listen to a range of music, but singer-songwriter music is what I listen to most. I do also enjoy the occasional 100db+ blast of a good rock or classical tune, but it is more the exception. The room is fairly large, but I sit only about 10 feet from the main speakers. I had been considering the ASL amp (as mentioned in an earlier post). The little ASL Wave 20's have been the most reliable tube amps that I have had, and have not even needed a tube change in over two years of 10 hours per day use in an office system.