my 2 bits... screw the equations about how much you should spend. don't buy a typical engagement ring (diamond solitaire) where the only difference is how big and nice the diamond is. buy something unusual, buy something vintage, buy something that you know she'll love and don't worry if it costs $50 or $5000. just make sure it shows personality and that she'll like looking at it for the next 50 years. for something unusual in pdx check out gilt on trendy-third and maloy's on 10th (by the 9th & yamhill smartpark).