Will I need a new converter or a header?

 

Magnaflow has some products listed as a muffler/resonator, if I buy one of those, do I not have to buy them seperate?

 

They are different things. Buy a muffler, buy a resonator. Resonators look like an exhaust pipe, but with a waffle looking inside to initiate the sound "deadening" (for lack of a better word). The muffler looks like a.. well a muffler.

In your case, it seems as if you would be better off picking up a WS2 or WS2 knock off cat back exhaust. I heard that Yonaka makes a decent WS2 knockoff and they are like $250ish for an entire cat back system.