Recommendation On Car Audio Components

I just bought a new car, Buick Verano, same size as the Chevy Cruze. I want to keep the stock 7" headunit/display and not install an aftermarket HU since it would need a lot of custom work to look right.

Here is my equipment so far:

RAINBOW CS 265 PROFI VANADIUMs powered by
ARC AUDIO FD4150

I have a Hifonics zx 6400 amp powering one IDQ12 D2 sub however I am leaving that in my old car.

For the Buick Verano, I am thinking about getting the Alpine 8" Single Ported Enclosure Loaded with a Type-R subwoofer SBR-S83V
Amazon.com: SBR-S83V - Alpine 8" Single Ported Enclosure Loaded with a Type-R Subwoofer: Car Electronics
and to power it I am thinking about getting the MRP-M500 - Alpine Monoblock 500 Watt RMS power amplifier Amazon.com: MRP-M500 - Alpine Monoblock 500 Watt RMS power Amplifier: Electronics

The reason why I am going with the above combo is because of the small factor, I like how the sub comes in a very small box and the amp is very small as well. What do you guys think of this combo?

One last thing, I need a good processor as well. I have found two:

Alpine pxa-h800 ($700)

jbl ms-8 ($535)

However I was told that the Audison bit10 is the best. What is the MSRP on that? I have not been able to find it online.