Anyone looking for a good preamp solution for their Toriis should make sure to check out the Dodd buffer. Its available in kit form pretty cheaply and sounds damn good with the Torii.
Compared to running the Torii naked I gain in soundstage width and depth, get a splash more sweetness and resolution and it MAY be a little more dynamic.
Its just a buffer and has no gain of its own and I recognize the changes I'm experiencing may be just impedance correction rather than what one would experience with an active pre, but two friends suggested it to me--one with a Torii 3 and one with a Mini-Torii, so I'm not alone in liking the pairing.
http://doddaudio.com/diy.aspxThe single input/single output kit is a laughable $150. Definitely worth checking out, IMO, though I'm using the full kit.