A little late to the party on this I know, but two points related to the topic at hand.
1) Find a broker in your area who sells diamonds. Dont' buy a ring from a mall jeweler. The lighting usually is such that EVERYTHING sparkles in a mall jewelry store. And buy QUALITY, not quantity. Explain to the girl that you could buy her an enormous piece of shit stone (that will still look pretty in the setting) , or maybe get an excellent quality stone (a little smaller) for the same price. Tell her-- your grandkids will one day appreciate the better stone, and so will she. Tell her you love her too much to buy her an enormous piece of junk. If money is no object---then buy both quality and quantity. I have a lot of money, and I could have bought my wife a huge 5 or 6 c. ring had I so desired, but instead she got a 2 c. colorless, flawless emerald cut diamond for the same money I could have spent on a much larger stone.
2) When it comes to weddings ---never forget this. I once had a priest tell me that couples spend a ton of time, money, energy, and effort on the FIRST day of their lives together as a wedded couple, and NONE of the same effort on the rest of their marriage. Great advice for any couple considering marriage! It would be much better spending the funds for an extravagant wedding on a down payment for a house, or investing it for your future together. Don't blow a ton of money on the first day of your lives together.