Are they really all that efficient Gene? SVS' product page says:
Sensitivity: 87dB (2.83V @ 1 meter full-space, 300-3kHz) If they're actually a 4Ω nom. speaker, 2W is made with 2.83V. So for an apples to apples comparison, the Ultra bookshelves should be docked 3dB for a net 84dB/1W/1m, correct? This figure would also gel with Butterworth's testing of the Ultra towers (87dB), centre (85dB) and surrounds (80dB) linked above.
There's a lot to like about these speakers though, and I enjoyed your forensic review.