I found the same Tang Band but in a 95dB version.
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=264-893
This would work quite nice....wouldn't it?
A great illustration of speaker design tradeoffs. The higher efficiency one has a shorter linear excursion (xmax) of 3mm vs. 5mm and a lower QE. It is clearly intended for ported boxes, while the other is intended for sealed boxes. The ported box would be larger (maybe 3 cubic feet instead of 2) but would go deeper.
They appear to be identical except for the thickness of the top plate. The higher efficiency one has a shorter top plate (you can tell because the excursion is 4mm less peak to peak, and the overall depth of the driver is also 4mm less). With the same magnet and voice coil, the field strength is more concentrated giving the improved efficiency at the price of reduced displacement. This way the cone and voice coil mass is not altered so the sound will be basically the same. Very clever bit of engineering, IMHO.
If it were me, I'd go sealed box if I was planning on a sub, because you can control excursion better, they are easier to integrate with a sub, and the box design is less critical. If I knew I would never use a sub, then I'd probably do the ported box.