re wire mach 460 for subs?

You have an easy install here. There are at least two ways to go, but both involve adding your sub and sub amp via the Alpine's sub out RCA's. The mach 460 can be wired into either the Alpin's high output speaker wires (using a $40 converter), or the Alpine's low level out puts using a RCA converter (scosche fd03). In all cases, you also need the power harness adapter (if you don't want to cut original harness). Some people even make there own RCA adapters.

Well the mach 460 system runs off of 2ohms and your headunit is 4ohms, It won't sound perfect but it'll sound nice. I don't see why they would have to re-wire so the subs worked. I've used a LOC with subs on the stock wiring.