I've used Gunbroker a bunch for common handguns and rifles, but I'd be hesitant to use it for an unusual sxs shotgun. In my experience, the Gunbroker buyer isn't generally a high value collector.
I usually do penny auctions with no reserve, as I want to sell what I'm offering. Generally, I've been pleased with the results. You can set reserves and minimum opening bids, but it seems that doing so significantly reduces interest in the item offered.
As for getting a gun from Canada to the U.S. if your buyer is here, I have no idea what the process might be. I've imported a gun from Great Britain (used British Sporting Arms to handle the transaction) and I know Steve Bertram, who posts here regularly, imports from there as well, but whether either could or would handle a shipment from Canada is something I've never asked.
