The Nikon D50 has the lowest sensor noise of the APS size DSLR's at the moment, after that the Pentax *ist. A lot of pro's are getting them for low light photography at weddings and events. I think, but I'm not 100% sure, it has long exposure noise reduction as well, this is a 'dark frame' amp noise removal that tries to eliminate the purple blooms you see around the edges of the frame when the CCD or CMOS sensors overheat during a long exposure. It takes a second exposure straight after the first but with the shutter closed so it can pick out the overheated areas and reduce the purple blooms in these areas. Whatever camera you end up getting, make sure it has this feature as it is a totally different issue to normal 'grain' noise that camera are usually judged by. Just found out tonight the D200 does this far better than my D70 did but the trade off is more 'grain' noise at higher ISO's. Nothing to worry about too much.
If you want to move up a gear and sell the family heirlooms, the Canon 5D should be superb for night photography.
