The shaker 500 consists of "upgraded" speakers (i use the term loosely) an amplifier and door "subs". The base system sounds absolutely terrible, a surprisingly embarrassing level of quality for ford to put out. In my previous mustang 12 V6 had the shaker and after replacing the door speakers it sounded reasonably good, however in my current 13 GT with base stereo I have replaced all speakers added a 4 ch and mono amp, added a sub, and a clean sweep. Next stereo project is to replace the head unit.
13 GT base, 3.55, Sterling Grey, MGW shifter, BMR LCA's, GT500 AB, silver RTR's, 275/40/19 Michelin pilot super sports, more stereo equipment than I will admit to, more parts to come.