We're in California and my husband bought my rings (e-ring and matching band - Jeff Cooper Designs) from Security Jewelers in Michigan. He said they were wonderful to work with. I think if you're going to buy online, you should go with a reputable company.
I should add that the jeweler supplied my husband with all of the details (4 C's) of my center stone before he purchased it. I believe he saw the GIA report before purchasing it. If the jeweler cannot do this, don't buy from them.
Hey I hope this works my last reply just disappeared.
My FI and I split from buying online and using a jeweler. He bought a loose diamond from Blue Nile. Perfect for him because they let you search by the four c's and other characteristics. And he loves researching.
Then I saw a ring that I like from a site called ringdesigner.com. But the site seemed a little fishy. So my FI took a picture of that ring to a local jeweler (NOT a chain, most of them won't set loose stones) and the jeweler custom made the ring and set the stone. The price was actually less than ringdesigner sold the ring for.
I would really recommend Blue Nile though. Their pre-set ring selection is very traditional, however. So if that's what you like they'll have it but they don't have really unique pieces. With any e-ring there you can choose any diamond in their database, so you get to pick the diamond that fits your budget. My FI has bought pre-set jewelry from there for me and I have really like that as well. They have nice customer service and an unconditional 30 day return policy.
Buying a diamond online we saved about $1500 for the size and quality of diamond we wanted which put it in our budget.