If you are retaining the Y-pipe then I would recommend using 2.5" single piping.
If you have the pre-cats or stock cat you could go with a bullet style resonator over a full bodied unit but either way still retain the rear muffler as well.
Magnaflow is a nice deep tone but a bit boomy.
Dynomax is more throaty/exotic sounding. (Think Touring car without the rasp)
Of course only use straight through design.
