Hello Everyone, I am new to this forum and would appreciate some advice if you can spare the time. I have been shooting DSLR for about 2 years with my Canon 20D. Mostly nature stuff, wildlife & macro. I use my photos for graphic design work and really need high quality photos for my work, hence my investment in L lenses. I currently use a Canon EF 70-200 f/4L for my telephoto stuff & EF 180 f3.5L Macro, but need a little more zoom capabilty. I have been researching the EF 100-400 f/4-5.6L IS as the next step up. I was dead set on purchasing this lens. However, I have "heard" and read some articles that this lens is not as sharp wide open. Was wondering if any of you have heard anything about this. The local store reccommended the EF 400 f/5.6L as an alternative since it is a sharper lens, but I would really like the IS and zoom capabilty. My alternative was to maybe upgrade to get the EF 70-200 f/2.8L IS with a 1.4 or 2X Teleconverter. Tried the TC on the f/4 I have and was not pleased with the results. Good option or overkill? Was budgeting about $1000-$1700 for this new lens, so if you know of any alternate brands that might flip the bill, please let me now. Thanks for all the help.