Any brand will work, doesn't have to be Scosche... Can be Metra, Best Kits, etc...

If you do a search, I posted up on using RCA's and splicing in at the factory amp in order to get subwoofer control and better sound Q from the fronts.

The RCA harness that they showed you, won't have any real benefit over speaker level other than some better sound quality... BUT you need to have a deck with a high Volt Pre-out (like 4 Volts and up) to properly get the same volume out of the amp...