I'd go with the Nikkor 85mm for your portraiture and some of the concerts (if you are close enough). I'd keep the D80 and try out a 70-200mm f/2.8 AFS VR lens on the D700. If you are happy with the performance of that lens on the FF body the by all means add that lens for additional concert and wedding use. If the 200mm is long enough on your D700 for your preferred usage, then sell the D80 - else keep the D80 for more effective reach from that lens.
Roger It is still ISO, aperture and shutter speed, right?