Yea, 5A sounds low to me too. But its what the manual calls for. I think it previously blew because I the wires touched for a couple seconds when they were live. We'll see about the new fuse.
And yes, I am running a couple small amps, one 100W to my front speakers, one 300W to my (2) 10's. Everything sounds great to me. So I can't realate to the underpowered speakers.
Well, the two stock ford speakers in the rear doors are running off the head unit. But I dont notice any distortion, since theyre stock and they suck. Best wishes.