It looks like now I can pick up a used, but well care for D300s for around $600. A new D7100 for about $950. For $350 difference is the D300s worth it? In other words - is the Af better than the D7100? Is the IQ significantly lower on the D300s? I would like access to the high frame rate and huge buffer. But I also shoot in low light sometimes - would that be a problem?