if you need heat, you are limited to heat exchangers with a new muffler on the end....a new Bursh is your best value, the Triad supposed to sound the best...I've never seen dyno comparisons between the mufflers, as far as I know, they all perform about the same, just sound, weight and looks are what seperates them...some people like the 4 tip ansas, since they like the all looks and no go
headers will give you a few more HP and gain some performance from a lighter weight assembly, bring cash, they "start" at $400 and go up from there really fast.
For headers, European Racing is more in your price range I believe (see vendor section) and if you do have money, the best is from CFR, the Tangerine Racing header...these start at just under a $1000 with no muffler included (I could be wrong)
Oh, and for a stock motor, all that money will gain you about 5hp if you are lucky on that motor.......of course if you are lucky, you won't break and exhuast stud removing the old exhaust if you go the header route, then start adding more money to the mix....