Is it that imortant to change the exhaust gaskets when putting on aftermarketexhaust?

[BavarianBeast]

Hello, I am about to remove the stock exhaust and catalytic converter from my porsche 911, and replace them with an aftermarket exhaust system and track pipes for club racing. The website in which i am ordering the parts offers a set of new copper gaskets for the cats and muffler for $40. I'm just curious, is it really worth the $40 to replace the exhaust gaskets??? Or should the old ones be reusable????? Any input would help.

http://www.fabspeed.com/911Carrera.html

thanks,
-Will