The jewelery business is such bulls***. TOTAL bulls***. There's NO way any ring of any size or style is worth 1700 dollars, unless it turns you invisible. How much food can 1700 dollars buy? How much FUN can 1700 dollars buy, for her, not just for you? That seems much more worthwhile than a stupid ring. Bring her sky diving, she'll never forget the experience! Hell, do ANYthing with that 1700 dollars. That being said, about a year ago, on my partner's seventh year together, I went out and sought help from a friend who is a jeweler, and MADE my partner a ring. It was nothing super special, a very classic Greek design made out of platinum; Very classy looking, and nothing to garish. It cost me a whopping $60 per ring for the time spent and the ringstock from which the ring was cut.
The most important thing I found was that making something yourself, designing something yourself, or something like that is much more personal. He knows how much I paid for the rings, and he doesn't care at all. It's more about giving a piece of ones self to someone, in my oppinion, rather than giving a large piece of ones paycheck. I could have purchased an expensive ring, but he was actually delighted that I didn't.
In short, don't think of it as spending money on YOU or HER; Spend it between the both of you. I suggest having said discussion with her. I bet you'll find she's more than amiable to the idea, and will enjoy the memories that you develop with her more than any ring.
I don't know, maybe I'm a bit biased, but if you're going to marry a lady, she should be marrying YOU, not a ring or a paycheck.
Sorry about the rant. =) Here's hoping for a long and wonderful relationship to you and your lady, hopefully including some skydiving in there, too.