Which Auction league provider do you use

[The_Idiot]

I am looking at going with an Auction league for the 1st time after 6 years of running a 12-team re-draft league using Yahoo.

What provider do you prefer?

12-team League
Head-to-Head Scoring System
I would like to be able to customize the scoring system.
I would like for the computer to handle "blind" bids on waiver wire pick-ups?

Does such a site exist?