Stock 300, with a few mods 400 is pretty easy. A few of my buddies have this motor running around with some Dinan mods in the 400-450 range.
It pulls like a proper I6. Over the summer my buddy and I were coming back from a boat delivery. He was doing about 90 in his 335 with about 410ish at the rear wheels, just lean on it a bit and 130 comes up nice and fast.
Proper car.
It actually has 320 hp @ 6000 rpm and 330 lb-ft @ 1300 rpm because the M Performance Power Kit(MPPK) is installed at the factory. But you are spot on regarding the way it pulls; turbo lag is essentially nonexistent. I would definitely install an LSD before I added any more power.