I really appreciate all of the help. I'm definitely looking to buy the right thing rather than focus on getting miles for it - I was hoping that I could have my cake and eat it too. I'm hesitant to make such a big/important purchase online and was leaning toward buying the ring/stone from CostCo (really good quality and great prices - lets me get her more for less) in Delaware (no sales tax). Since CostCo only takes AmEx, I'll probably put it on an AmEx that gets points and do a balance transfer to a 0% card. I really have to spend some time looking into the stuff that you all have posted since there's a lot to consider. I don't think I thought this much about the purchase when I bought my car!

Many thanks for the tips and the well-wishes!

peace,
~Ben~