The 2600Pro is definitely not an upgrade from a 7600GT. More like a slight downgrade actually.
For $90, you can find a decent 8600GT on Newegg, and this would be s slight upgrade from the 7600GT. Not worth it. If you are on a tight budget, save your money for the 8800GS that is reportedly coming after the 8800GT, according to what I have seen on Fudzilla.com.