I will say this at the risk of peeving off some true D7000 believers, but I would bet the image quality and low-light performance of the D300 are just as good as the D7000. And I am tired of hearing about specifications. I know all the numbers. Most of the putdowns about the 300 revolve about it being "Old Technology." Well, in a couple of years (or less) you will start hearing the same thing about the D800. And it will still be a great camera. So is the D300. And the D700 for that matter, which is now considered old, too.
The D7000 is an excellent camera. So is the D300. They both make great pictures. It's still the painter, not so much the brush.