With the magna flow that came with it, and a high flow cat, it's pretty loud. A resonator or 2 should quiet it down.
Temporarily, I'm running a cheap $30 turbo muffler from Summit, and a resonator core tip, and it's fairly quiet (the engine is louder than the exhaust at idle).
A 1g exhaust will fit, it just needs to be extended between the cat and the first bend.