I used Modaselle for selling my Chanel flap handbag. I had sent in a few quote requests to their site, as well as a few sites in US (i'm in Canada). The quote request form on their site was very simple to use and they got back to me the next day with a very comparable quote to the US stores. Perfect for me since I didn't want to deal with potential US duties and fees. Also just like some of the big US sites, they sent me a pre-paid shipping label so the whole thing was free. I sent it in, they got it, honored the quote and sent me a check the next day. I was very happy with how quick and painless this process ended up being.
One other thing to note - they don't currently do consignment so it's just for buying or selling.