My husband and I highly recommend Shane co.
We've gone through them before for our rings and found the quality exceptional, especially compared to other diamond stores. Not only was the price lower, but the rings seem to keep longer.
We got our ring set from Shane Co and ordered a loose Canadian diamond from a different source, only to find out that the diamond didn't fit our original set and it needed a new mount to be set to fit it. Even though we didn't purchase the diamond from them, they mounted it for free (in two days no less!) and not only allowed us to keep the warranty on the original set, they warrantied the diamond for free.
Even better was how beautiful it was when they were done. It was a much larger diamond and really didn't look like it would fit well in the ring and would look off. They assured me that not only would it look great, but they would place it down as far as possible. When I got it, it was BEAUTIFUL! It sits down as low as possible, is very secure, and absolutely beautiful. Did I mention it was beautiful?