Hi Wes,
Congratulations on getting ready to pop the question.....how exciting :) Here's what I might consider if I were you. If you shop at Blue NIle, you can get a white-gold ring with channel-set or pave-set diamonds (small diamonds inserted into the band) between $550-$800. This would leave you about $3,000-$3,5000 for the stone.....allowing you to get a stone that is larger...as large as a carat even. White gold has the same appearance to the naked eye as platinum.....the one disadvantage of white-gold is that every few years it needs to be re-plated to maintain its luster (which is an inexpensive process that can be done at the local jewelry shop). If you feel as though you must go with platinum, than I'd go for the simplest band, so that you could spend more on the actual carat size of the stone.....i think this is what draws the eye most when looking at a ring. Most girls who I've talked with like a stone to be close to a carat, if possible. Don't worry about her fingers being too small to carry it off....the stone size won't overwhelm her finger.
