Plitron is a company which makes toroidal transformers. This information is from their web page:
http://www.plitron.com/advantages.asp
High efficiency of around 95% at load versus 80% for a standard transformer.
Size can be 50% smaller and lighter than conventional transformers.
Toroidal transformers are acoustically silent with very low mechanicl hum compared to conventional transformers.
The windings of the toroidal transformer act as magnetic shielding and they radiate 1/10 the magnetic field of conventional transformers.
The toroidal transformer uses 1/16 the power when no load is being driven.
All of these factors should be of greater importance when larger loads such as 1000 watts or more are required to drive the speaker output amplifiers.