Looking for a nice rock for an engagement ring. I want to know what quality limits I should be looking for in this application. For example - in the real world does anything better than an H or I make any difference? What about an SI1 or SI2? And what cut quality?My guess is that there are some rules of thumb that tell where the sweet spot is that will give me the best eyeball look for the $.BTW - I am in the $10K to <$20K price range.