Here is another crazy idea to get greater image quality, if you can live with the down sides. Use MF lenses and adapters. I have a few L lenses, have had L zooms like the f/4 17-40mm and 70-200mm versions. I have gone to L primes like the 35L and consider getting a 135L, mostly for the indoor basketball I do. Last season I used the 35L and an 85/1.8 with good success on my 5d. But most of what I do is travel, scenic stuff and have decided to go with MF primes. Why? Cause they are light, sharp and this stuff doesn't move. I can take the time to focus manually, heck even use a tripod mostly. I won't get into a discussion of what type but suffice it to say, these lenses can be relatively cheap also, and there are adapters for almost anything short of M Leica lenses. I have used my old MF Nikkors and other old primes without much issue. IN general, most of what folk have said above is true, lenses like 28mm, 50/1.8 or 2.5, 85mm primes are excellent and very sharp and give up little to L glass. They certainly can match or excede some of the L zooms in many factors. The only difference between these and the expensive L glass, besides the cost and weight, is corner sharpness, CA, and even here they in some cases can be better[heresy] then the L glass, in others not so much, but one thing for sure, I am leaving my heavy zooms home on next trip.