ok so the amp is an orion 1200d (725W@2ohm) and the subs are 2 ascendant
audio atlas 15s (wired to 2 ohms).  I was playing with my gains because I
can't really find the point where i get a clipped signal.  If i turn the
head unit up past about 50 (of 62...pioneer p7700mp) i can hear the
distortion from that but with the volume on 45 and the gains turned up i
never hear distortion.  I'm scared to leave the gains this high so i usually
leave it at about 5/8 since its plenty loud there.  So while doing this, the
amp just quit, i found the culprit, it was the 80a agu fuse, but it wasn't
blown, no burn marks, but i tested it with the ohmmeter and it definately
didn't have a connection.  I  broke the glass and one of the small caps fell
off the end so i'm left believe the fuse shook loose but this seems
unlikely, is it possible it got too hot and came loose?  I am running 4gauge
wire and the mentioned 80a fuse, that should be sufficient for the amp,
right?

so my main questions are...
Is distortion from gains too high on the amp any different (in sound) from
distortion from volume too high on the head unit?

Is the wiring setup ok (big enough wire/fuse)? And should i worry about the
fuse or just replace it and go on?

i have some fuses ordered as i couldn't find any locally, hopefully i won't
be without my bass too long

lastly i've heard that with the xbl^2 motors its much harder to detect
distortion, any validity to this?

Thanks