Good info, guys and appreciated by this newbie - thanks.

Any comments on which first mod might give the best bang for my buck:
1) a nice cold air intake (maybe an AEM V2)
2) upgrade from a stock exhaust to a cat-back
3) header upgrade (say to a 4-1)

Reason I'm asking is, maybe the money I'd spend to upgrade the OEM-replacement muffler to a nicer performance cat-back would be better spent elsewhere. Factor into the equation that I need to replace my muffler regardless of whether I buy a nice one or an OEM-replacement type.