basically what im asking is is it possible to still hook up an amp with a single 12" sub. And if so, what am i going to need. (besides a scosche wiring kit)

 

if you are just powering an amp for your sub you will be fine. If you want to have another amp for your speakers you won't have enough outputs.

 

he could actually get y - splits to add 2 extra outputs, buts its not recommended.

 

all his speakers would be on 2 channels... I can't imagine that would sound very nice, and less espensive than splitters would be depending on his amp he could use the rca outs if his amp has that... usually its the other way around. I know my buddy has his 4 channel and then a pair of rca outs to his sub. that'd save him from running 2 sets of rca's. heck he could even put the splitters on the rca out on the woofer amp and then he'd have 4 rca's to plug into a 4 channel

 

Just wire the dash/door speakers to the head unit. Run your rca's to your amp. And run speaker wires to the amp. I'm assuming you know how to run the power and ground wires for the amp.