I regularly have shrimp and fish up for auction on Canadian Aquarium Connection Auction and, more recently, Aquabid. I enjoy the CAC auction; it's getting more active both in selection and in bids. As a livebearer geek, it is THE Canadian place to go for non-standard livebearers and locally produced foods.
That said, I doubt there is enough traffic to support 3 auctions.
Part of the charm and value our classified system is the interaction between members. I know the mods are always admonishing us to stay on topic, but, honestly, I have learned SO much from the commentary in classified threads, and the conversations it's spawned. Auctions are very impersonal. Many sellers don't even respond to requests for information or post (i-trader type) feed back.
(for the record, I'm not a professional "breeder", and I don't breed to make money (as a 'for-profit' venture, my hobby is a resounding failure

I do, however, end up with more babies than I can house. My colony set-ups are mostly self-sustaining, and there are extras. I give lots away for free, more yet in trades with BCA members and I sell
some.)