Replacing the muffler is really all that is needed for a deeper tone. there are several differant ways to run the pipes into the muffler(s). you can do a 'Y' pipe and use two mufflers.. you can use a muffler with a single inlet and dual outlet and have the inlet go in through the side. and with both you can take the resonator off. yes the GT-R is expensive but its really high quality materials (i do not have the system) but to answer the initial question; yes, just an aftermarket muffler will do the trick.
Exterior-AVS window and sunroof wind reducer, Dual Exhaust, Tinted tails, 35% Tint all around, DDM tuning 8k Highs & Lows.
Interior- Red LED's
Performance- CRAB's Option 3, Exhaust
Coming up: MMI's, Painted Calipers, Painted Side Mirrors.