Hey buddy,
I own a Nikon D60, so have I tested D40 to D80. Compared to D60 what D80 have is the image stabilization and extra focal points, that can add image clarity than D60 or ofcourse the previous ones.
Regarding night shots, D80 can help you shoot good shots at high ISO as much as D60 on a tripod (I used a normal Non VR lense). ISO range is same for both D80 and D60. They range from ISO 100 to ISO 3200(both cameras have this range of ISO). I am very happy with D60 as it was so cool when I got a noiseless image at 800 ISO (normally at high ISO image may contain noise of fine grains).
another thing about D60 is its weight, D80 is not that easy to carry stuff when compared to D60 (not too weighed any way ;-))
You can buy an additional lens for D60 for the same price of a Nikon D80.
D60 camera + D60 kit lense + any additional lense (extra) will cost almost equal to Nikon D80 Body + D80 kit lense
Altogether, I suggest you D60, but D80 is also not bad, if money is not a concern, u can go ahead with D80.
:-)