I have a high powered radio that runs the 4 door speakers.My 4 channel amp i use 2 channels to run a set of rear component speakers and bridged the other 2 channels to the sub.You are trying to run 4 speakers and a sub off of 1 amp?You can do it with a 5 channel amp the only problem is they usually arent small so its hard to find room for it.I am eventually going to add another amp for the sub and add 2 more component speakers up front.I am not sure if i can help you but if you want email me at
wb605@msn.com and i can try.