Toroids, where's a good place to get them?

I want to build those dual mono kits from audio sector, but I don't know where to get the toroid transformer that I need. Where's the cheapest place to get them. I'm not sure how much power I should put into the chips, they say it takes 20-84V but I'd like the opinion of some of the more experienced amp-builders on what voltage to use.
I would scour the surplus dealers before going retail. Toroid transformers are pretty expensive and you can save some real money by buying surplus.

Don't be afraid to buy a transformer that is too high or low voltage for your design. You can always add or remove wire to put the voltage right where you want it, and you can easily add windings for additional voltages. Just make sure the transformer has a large enough core (VA rating) and proper voltage primary windings.

It looks like Plitron Canada has some good surplus:

If you aren't dead set on a toroid, a pair of these would work for a lot of audio amp circuits: