Look around first.
www.nipponpower.com
www.jgycustoms.com
www.240sxmotoring.com
www.cipmotorsports.com
www.phase2motortrend.com
Those are just a few. Look on our FAQ page for some more. I have the Apexi N1 and it sound really good. Its only loud if you punch it, but not ricey loud. If it is too loud for you, order a silencer. I've heard lots of good things about the duals and they do sound pretty good. Its Apexi, countless hours of research. One of the biggest names in the industry. That exhaust only comes for 240s and rx-7s so I would imagine it was basically designed around the car. No worries, it will sound a lot better than those shit-cans from Autozone. Welcome to AF. Read the guidelines, the FAQ, and have fun.