Review compared to fastest Nvidia card described in your post:
For gaming I would go for the 7700 but if it costs a lot more then the X1600 get the X1600 then. The performance difference is very small. The 7700 is made at 80nm compared to the X1600's 90nm so it should stay cooler and take less power. Dont go for the impaired 7600SE. The 7700 is a 7600 but then a little bit tweaked so the 7700 is better.
For watching video, the X1600 image quality is better then all the nvidia cards you described so if you are a quality buff go for the X1600. The quality is better in gaming to but youll really have to look to see the difference.
So in short it depends on the costs, if you have the cash then 7700 would be best.