Ok...well you should definatly get a full cat-back since you will be restricting air flow with new headers and stock piping coming from your cat
also if you want to find cheap cat-backs go to
http://www.groupbuycenter.com
and if you have friends that are looking into buying a cat-back then you will get it at a group price which is a lot cheaper...also it does'nt matter if they have a differnt car or even ordering a differnt type of exuhst as long as it is from the same vender you can usually talk them into cutting the shiping price down a little if you order a larger quanity
well have fun and happing hunting
Chris
ps:
http://www.modacar.com also has some cheap prices