If I had to guess (since I've not heard the Sunfire sub), I'd think it would be better at music reproduction without the boom factor (since it's a sealed enclosure design). Those designs are also often rather inefficient, but Bob seems to have countered that by including a ridiculously powerful amp to drive it. 8-)

If you're into the theater aspect mostly, then I'd say you'll probably get more output out of the LFM-1, even though it's got a "smaller" amp because of its inherently more efficient design.

Given your choice of KAV-250 amp for your mains, I suspect you do a lot of 2-channel music listening so you might be more interested in something that does music better while sacrificing raw SPL numbers.

Cheers,