I have a 2005 Bonneville GXP and I am looking to install an aftermarket pioneer player in it and a set of subs. I know that I need and interface, but I am searching for some knowledge on what one is better, and are there any tricks to installing it so that the steering wheel controls still work. Thanks. I am new here so any help is welcome.

Crutchfield.com can give you stereos that will work with adapters that plug into your existing wheel controls and work.

On another note, you are better off replacing ALL of the speakers and bypassing the Monshit amp and just going with a nice 4 channel amp and a mono amp for your subs. Believe me, your ears and chest will appreciate it.