I've continplated going this route. Bluetooth and amp enclosed in waterproof housing (it's a boat speaker) so I'd just have to run one line of +- remote to the battery.
I especially like the simplicity of it. Using the phone for playlists (pandora) and volume control.
To be completely honest, I bought this already back when I had the P500, but it was physically larger than anywhere I could mount comfortably. Although, I almost pulled it off.
But that was then. This is now. I've got more overhead locations. It was unbelievably LOUD and the 6x9 gave good mids & lows for hearing over the motor.
I sent it back the first time (P500) but I've since thought about buying it again. (Or something closely like it)