Any of those systems will do the job. Simply stepping up from your Canon A620 to a digital SLR is going to make a big difference because the noise levels will be lower even at high ISO settings. If image stabilization is important to you, then I would encourage you to look at Pentax, Sony, Samsung, and Olympus. They're all making digital SLRs with built-in sensor-level image stabilization. That means you won't need to buy special lenses. No matter what lens you're using the image stabilization will be available for you.