A mass 2010 S24 (Vd 1.4L, Vas 40L, Fs 25hz) in a 13" cube (outer dimension, say 3/4" mdf construction with some 1/2" bracing, net volume right around 1ft^3), 100% stuffed, tuned somewhere between 20 and 25hz with a pair of 12" PRs. If I've managed to start to understanding specs right this should come pretty close to the performance of an EBS PR Shiva not? Just cost more and require a chunk more amp power. But it would be tiny. Edit: Just occured to me, I really don't know how PR specs relate to tuning abilities. Could a pair of 12 PRs tune an enclosure that small to under 25hz?