If you are interested in playing big budget action games like shooters or RPG's, then no, I wouldn't upgrade. Almost all of those types of games that historically were PC only are now coming out on consoles either first, or even worse, exclusively. You might consider saving the upgrade money and putting it towards a console and HDTV to play it on. If you like MMORPG (WOW, for instance) and RTS games then you should upgrade, but even then, I wouldn't go crazy on specs.
do you want to play things on max, or are you happy at med-low settings? i assume the latter, cos the 7600 really is starting to.... umm.... (thinks of euphemism for being crap....) "lag a little at higher resolutions" (crysis would absolutely brutalise it).