So far I have the 18-105 VR and the 50 1.4. I kind of want to get something wide angle, maybe a 12-24, or a 14-24. Of course, 2.8 is preferable, but which ones are good for the price? I'm not looking to drop too much on it, so the Nikon 12-24 2.8 is out. Budget is up to about $500. Any suggestions?