I am a professional photographer...
I use a Canon Rebel XTi for concerts... the camera at 1600 ISO is plenty fast enough with the right lens.
The XTi shoots 10 meg RAW files, which are good for 11x17 posters.
The CMOS chip in the XTi is now self-cleaning.
The 1.6x is smaller image area than a "full-frame" 1.0x camera. That means the image is slightly cropped, so you just adjust your picture framing when shooting. To get a full-frame camera, you jump up to the $3K price range.
Many people say the 1.6 crop factor in the CMOS chip is a limitation. For concert photography it is actually a benefit.
The 1.6 crop factor makes your lens "longer", meaning you can zoom in closer.
read this and it will make more sense:
http://www.kenrockwell.com/tech/crop-factor.htmSpend you money on quality lens, the camera is not the most important part of a setup. A really good lens on a Canon Rebel will give you great shots. The Canon EOS Rebel XTi shoots very nice photos, with good color rendition, broad dynamic range and accurate automatic white balance.
Here is a picture of Warren with a Rebel XTi using a Canon 80-200mm f2.8 L lens (image is shot at 1600 ISO at f4.0 at 1/80 sec). The camera cost $600. The lens cost $1800. The quality comes from the lens... the picture you see here is at 20% of the full resolution.