I have ordered from Bidz.com and all their jewelry was quality built, very beautiful, and the items I bought on the auctions were delivered very quickly.
One thing to think about to get the best auction prices - do all your auction bidding in the middle of the night. I'm not kidding. You get the best prices then. During the day you will get left in the dust. An item can start at $1.00 (they all do) and within 2 minutes be up to $50.00, whereas during the night I bought the same item for $12.00.
Check them out for the best jewelry.