depending on your current set up, and what you like to shoot would influence your decision on the wide angle. 17mm isnt very wide on a 1.6 crop sensor (if that is what you have), yet i know that the 17-40 is pretty much the best lens you can get covering the wide to "portrait" focal lengths - similar to the kit lens you get.  10mm is another ball game - i think mayda has the 10-20 sigma so check some of her shots as to what the width of it can do.. other than that check out FredMiranda and see what people have to say:

http://www.fredmiranda.com/reviews/

"In every colour, there's the light.
In every stone sleeps a crystal.
Remember the Shaman, when he used to say:
Man is the dream of the Dolphin"

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