Well here is an update, in case anyone is reading this.

I have purchased the above equipment as well as: Polk PA660 4 Channel and PA880 Mono Amplifiers.

I have bridged the PA660 into two channels running the front splits and the rears are just connected to the head unit.

I found an old Jamo Sub 300 in my garage which had it's built-in amp fail (old HT sub) and I wired the driver directly to the PA880. I am still thinking about a new sub, but this one will do for now.

The whole setup is rather loud and sounds much better than I expected. Also there is no unwanted noise coming from the speakers (like the "hiss" sound or the whine of the alternator).