Thank you, Gonk, for your quick reply. You are of course correct to wonder about how these measurements were taken. I don't know how much of the article in question I can copy consistent with the copyright laws, so I am instead posting the URL where you can find it:

http://www.hometheaterhifi.com/volume_13_2/outlaw-lfm2-subwoofer-5-2006-part-2.html

I will certainly look into the two new subs you mention, for which I also thank you. Buying speakers, or any other audio equipment, online, with no opportunity to hear or compare it with comparable equipment, is really unsatisfactory, but obviously necessary - I know of only one high-end audio store in Tucson, a city with an MSA approaching a million people, and it does not allow home trials (except for a very short period and with a punitive restocking fee). Speakers, especially subs, are very heavy and therefore very expensive to ship, so "free" trials are scarcely free; buying several subs to compare, and then returning the losers, would be very costly indeed; and few people have switching facilities at home. But of course you know that, as does everyone in these forums (fora?). We must do the best we can, which is what I am trying to do.