Thanks all for replies. I am already using the max pixels avail for D300. Each of my photos are usually 6+ mb size.
I will try using spot metering next time to see if I can get better results.
Normally I do my exposure corrections in adobe lightroom, so I tend to just capture the moment and then correct later.
I am just surprised that due to exposure, the noise can be so obvious
Any tips on what mode to use for best exposure? I normally use Aperture mode.