You should have used the Arc Minis. I had 3 (2 125.4s and a 500.1)under the hatch floor in my old GTI and still had the spare and they never got all that hot. Plus, you could fit at least 4 of them in the same space as the KAR amp so you could have more power and be able to stagger the power. For example, I had 75 to each tweeter, 75 to each mid, 250 to each midbass, and 500 to the sub with no rears.
In your setup you really only need 6 channels unless you want to run the subs in mono and then you only need 5.