Hi Stuart,

I've heard good things about the Tamron 17-50 f/2.8 non-VC and not so great things about the Tamron 17-50 VC. Do you have the non-VC lens?

Regarding MI and MII. If you get a good deal on a 24-70 f/2.8 Mk I, I'd be very tempted by that lens. Keep in mind that 24 mm on a cropped sensor body isn't really that wide (59 degree Angle of View on crop sensor vs 84 degree AOV on FF).

General purpose lenses for a crop sensor body that I'd recommend include the EFS 17-55 and EFS 15-85. But I have read and seen great photos from the Tamron 17-50 f/2.8 non-VC. So, if that is the one you have, you may want to work with it a bit.