Will the "trunk" line handle the added current draw??? What size (ga) cable is there currently and whats the potential current draw of the 2 amps. Is the circuit protection at the battery for the current amp able to handle a 2nd?
"Antenna wires" - I'm guessing you mean the RCA cable? If so, best to run another set from the head unit to the 2nd amp. Most head units will have at least 2 RCA outputs.
I think he means the remote wire. What I've always done for the remote wire when adding a 2nd amp is just run a wire from one amp to the other so you'll have a remote wire from your head unit to the 1st amp and then a wire from there to the 2nd amp. Sorry if that doesn't make sense I've been drinking