I've just spent an hour reading reviews on the web about the T-Amp, mostly because I still cannot believe how good it sounds, and the one constant (besides how good everyone thinks it sounds) is the recommendation to use high efficiency speakers. 92 or 93 is where all of the reviewers seem to end up as a starting point.
But, given all that, I have been using it out back while building a deck with an old pair of Polk M3II's that are only rated at 89db sensativity, and it sounds absolutely fine.

Axioms; For when you've just Gotta have More Cowbell! 60s 150 350 8s 2is RX-V2500 DVD-C750 2900