I think that your first priority is to decide whether or not you really need full frame and whether it is in your budget. The cheapest FF Canon is the (discontinued) 5D.Originally Posted by AmirVscas
The following lenses on your list are NOT usable on Full Frame:
Canon 17-85mm f/4-5.6 IS
Canon 10-22mm f/3.5-4.5
Tamron 17-50mm f/2.8
Tamron 18-270mm f/3.5-6.3
Tokina 12-24mm f/4
(and the 18-55 that came with your 350D)
If I were you I would forget full-frame and look rather at a more modern crop body that does high ISO better than your 350D.