Need some advice. I am going on a road trip (kind of last minute) and would like to buy this lens extender (going to yellowstone - want to be able to zoom in nice and close).. so I'm looking at buying this [ame=http://www.amazon.com/Canon-EF-Extender-Telephoto-Accessory/dp/B00009XVBY/ref=sr_1_1?ie=UTF8&s=electronics&qid=1279913177&sr=8-1]Amazon.com: Canon EF 2X II Extender Telephoto Accessory: Electronics[/ame] to help me get closer pics of bugs/birds/whatever wild life goes by. I have read the description of the product, and my noob-ness is forcing me to double check with people on here who are more knowledgable than I am about whether my camera/lens is compatable with the product/all features of the extender.. the part that worries me is where it says "Maintains autofocus with any EOD body with f/2.8 or faster aperture" now since it said EOD body I currently have [ame=http://www.amazon.com/gp/product/B0012YA85A/ref=oss_product]Amazon.com: Canon Digital Rebel XSI 12MP Digital SLR Camera: Camera & Photo[/ame] (the 10.1 MP version though).. now I see my camera as EOS.. so I'm assuming the EOD isn't compatible with this.. if this is the case - can anyone suggesta lens extender that is compatible with the rebel XSI? I would be using this lens mostly with it. [ame=http://www.amazon.com/gp/product/B0007Y794O/ref=oss_product]Amazon.com: Canon EF 70-300mm f/4-5.6 IS USM Lens for Canon EOS SLR Cameras: Camera & Photo[/ame] Thank you very much for taking the time to assist.