I apologize if I'm putting a damper on the congratulations, but it sounds exactly backwards: it seems like the reason to start a shopping site in a vertical should be because you have insight or value-add in that vertical, not because you own a domain name.
No question. But ultimately the underlying value of the service is what determines whether it matters or not.
If you wanted to win a significant share of the search engine market, which would help you more, owning search.com, or designing a search engine that was actually better than Google in a way that users can perceive?
No - ecommerce is about connecting buyers with sellers. The domains capture the intent, auctomatic provides the inventory to take advantage of that intent.
Powersellers used to be tied to eBay, now they can connect to huge vertical audiences that are tied to their intent to purchase hence increasing their sales. Makes a LOT of sense this.