X-bit labs has an article on voltage modding the NVIDIA GeForce 7600 GT:
Products on the Nvidia GeForce 7600 GT chip haven’t been long on the market, yet have already gained recognition among people who appreciate inexpensive but fast graphics cards. The era of various versions of the 6600 GT has come to an end. Not that the 6600 GT is obsolete now, it is going to do its job well in a lot of computers worldwide, but it’s now time to meet the new best buy from Nvidia. The 7600 GT is an excellent product as is testified by numerous reviews.