Talking to some lady friends about this and if you are wanting to save some cash I'd suggest looking into lab created diamonds, or better yet hybrid diamonds.
HYBRID DIAMONDS:
The most beautiful and affordable diamond alternative on the market
Mimics the look of a mined diamond because it is infused with diamond
Large selection of shapes and carat weights ...countless possibilities.
Unmatched beauty: D-F color, VVS1-VS2
Individually cut to the highest standards
4 out of 5 jewelers can’t tell the difference
Adored and owned by celebrities you love
Diamond technology also used by some of the worlds most prestigious companies
Free shipping, warranty and trial period
Only $358.00 per ct. 
Check it out here:
http://www.miadonna.com/t-diamond-hybrid.aspx