The ATI HD 2600 is definitely a substantial upgrade to the 2400. And would certainly be worth it if you regularly exceed the 2400's maximum capabilities.
Unfortunately there is a bit of drama involved. You'll have to update your firmware to get the system to recognize the card. Though that shouldn't be too difficult, as the system should prompt you with the download upon installation.
Otherwise it's nothing that can't be found with a quick google search.
Here's the Guide on how to install your new graphics card if you want it:
And good luck.