JBA Catback exhaust is a good quality exhaust and it isn't very loud.
2004 to 2006 Nissan Titans have a restrictive stock exhaust and there is no question about it. In order to get the best performance you would need a 2.25" y-pipe and a flow through muffler, such as Magnaflow. The 2.25" y-pipe will be good even after you mod your Titan with a tune, headers, etc. If you plan to install cams, you can actually go up to a 2.5" y-pipe because you will be adding a lot more air flow in to the picture. Do NOT EVER go with a 3" y-pipe, such as the one found on Banks, because the pipe is too large for the gases to heat up and expand. It will kill low end power, period.not sure what the best recommendation is for Y pipe replacement though.