I recently purchased a 0.63ct G SI1 diamond certified by IGI for $2250. Now I am told that IGI certified diamonds are not as good as GIA or AGS. Is this true? I purchased it at a local jewelry store and thought that it was pretty good deal after looking around for a couple of weeks. I've tried to compare to diamonds on the internet and found similar stones for anywhere from $50-$400 cheaper although it is difficult to find an identical stone. The store has a one year guarantee if a lower price is found on a similar stone, but I don't know if they would honor an internet comparison. Any opinions???