Hello bsevag, and welcome to the CameraLabs forum!
Mehrdad has already given the right answers. Let me just add a remark about IS: It helps to avoid camera-shake reducing the IQ and thus you can
expose longer, what is very helpful in low-light conditions. BUT
it doesn't help with motion blur. So if people in the night-club are moving you cannot reduce the shutter speed say beyond 1/60 sec without risking motion-blur
So only two thing will help if you're under low-light conditions and want to avoid motion-blur: High ISO (800 or even 1600) and/or a wide-aperture lens, like a f1.4 or f1.8 prime lens!
So you should be looking for a camera that has low noise at 800 or even 1600 ISO (see Gordon's tests). My favorite in this respect is the Nikon D80.
B.t.w.: Motion-blur is not neccessarily evil - it may even give your pictures a special atmosphere.
Abbreviations and explanations see here
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