cat-back

will it make much of a sound difference just to put a cat-back system on the cobra or do i need to save until i can do headers and a mid pipe also. and does anyone kno where i can get a decent sounding exhaust that i can install myself for under $400?
 
Depends on what you get. Some catbacks are louder than others, some just louder than stock.

It really wont get too loud untill you swap the midpipe out though, thats were all the sound is at. A catless midpipe will be the loudest. A catted mid should open the sound up a little as long as there are only 2 cats, not 4 or whatever is stock.

Headers change tone moreso than make noise. Yeah, it will turn the volume up a little bit, but not as much as a midpipe/catback.
 
If you have stock, or shorty headers you want a regular (the larger) mid pipe.

Mac offroad H and their catback sounds awesome. So does a Mac H and a Flowmaster catback. You really cant go wrong with either one.