I'm starting to get the itch to upgrade the lenses for my Canon Rebel 2K. Currently I have the stock Canon 28-80 and 80-200 set--no USM or L series etc, just the basics--and a Sigma 105 (2.8) macro EX that I use for portraits and macro work. The Sigma's a keeper, but I also want to extend the range to a long zoom and maybe pick up a slightly wider max aperture. I'm considering a combination of the Sigma 24-135 (2.8-4.5) and 135-400 (4.5-5.6). These are not EX series, but are aspherical. Would this be a wise move or is this more of a "side-grade" than an upgrade? I'd like not to have to add a third lens (e.g. 200-400), but am concerned about the extra weight and expense of the Sigma set relative to any improvement in picture quality and convenience. Any thoughts? Has anyone else done this? Thanks.