We have two Sol GXP's. Mine is a coupe with the HFC and Solo Mach Shorty, stock outlet location. The Mrs has a roadster with a HFC and Magnaflow with a 3" inlet fitted in place of the 2.5" from the factory. The sound of the two is a bit different. The Magnaflow is a bit mellower, not quite as loud. The Solo has more bark, but not to the point of being obnoxious. Neither system exhibits unpleasant drone with the top in (coupe) or top up (roadster). The Rear Center Duals seems to be the system with the most reported drone.