Auctiva is nice as a listing service, but I would not use it as a store with its own domain name and such. Mostly because of the hosting.
Auctiva is only connected to the internet through Cogent, which almost every year disconnects networks (disputing of internet peering). I have been unable to use Auctiva or visit Auctiva stores for more than a week now. This forum works because it is hosted elsewhere..
Now your items are harder to find, than if you had an eBay store. As eBay is bigger and better secured against internet partitioning.