I'll be wanting to buy a portrait lens soon to go with my Nikon 18-70 which i love, and i've been told to look at the Sigma: 105mm F2.8 EX "DG" AF Telephoto Macro and the Tamron: SP 90mm F2.8 DI 1:1 AF Macro ? Does anyone have any experience with these or any advice regarding their performance ? I know i've asked this sort of question before but i want to make sure i make the right decision before i part with my money ! thanks for any help.