you can but its better to have your amp fused at the battery and have a seperate radio lead so it can be fused at the battery. some peopel fuse at the radio but i had a amp wire start on fire 7 years ago in my '78 ford. if i had fused at the battery and not the amp it would not have happened. killed most of the interior (i was working) but someone told me and i put it out before the truck recieved any real dammage to the truck. small 2 pill NO-NAME was lost along with a cobra 148gtl. i still dont know why the wire started, it must have shorted somewhere (casing was long gone when i got to it) but i didnt have it exposed anywhere, i came into the cab threw the firewall with a gromet, it was not exposed to any sharp edges.
oh well live and learn, now the radio is fused at the battery and i have a large 2 gauge wire fused from the battery into the cab with a fused distrbution block 1 terminal is for my subs, and the other was for my amp (i run barefoot now). i also ran a 2nd 4 gauge wire into the can for the 4 channel amp for my doors and rear speakers.