New mufflers or x pipe???

[S2STANG]

Well apparently I'm a dumb ass. My sitcker says nothing about exhaust. The other 380R I was looking at had the magnaflow exhaust.

What would be better for power and sound? I was thinking an x-pipe would give some more power and some sound with the stock GT exhaust. Would just changing the mufflers give any performance gains? Will the x-pipe be beneficial with stock after-cat? I have read that x-pipes give a world of power and sound when combined with an after cat system, but haven't heard anything about a pipe and stock exhaust. Mufflers are much cheaper than a mid-pipe...I don't know