I am looking to purchase a wide angle lens for my canon xti. (will eventually upgrade my camera body so I'm looking for a digital/film interchangeable lens in case I end up with a full format down the road) I have the 'stock' 18-55mm lens that came with the xti when purchased. I am also getting ready to purchase a 50mm f/1.4. Just invested in 70-200 2.8 L series... (wow!) And now looking for a good quality super-wide, preferably f/3 or better with sharp images ...BUT... due to my most recent "L investment", the budget for this wide angle is under $300-400... are my desires possible for this price -- any suggestions?