I assume you're already familiar with diamondbistro.com and loupetroop.com? These are consumer-to-consumer sites, so they're not curated like JBG and LAD - it's definitely buyer beware. But PSers often use these sites to sell jewelry they're no longer wearing (etc). Note that much of the jewelry sold on DB in particular has diamond simulants or lab-grown stones. It should be categorized as such, but you should ask questions if you see a stoned identified by a name you don't recognize/