I am getting (4) 15 XL M2s and I originally wanted to power them with a 12K but, I was informed that they are being discontinued so... Should I go with a single 9K or (2) 5K amps? I'm building a daily set up walled at the C-pillar in my Envoy and I plan on tuning around 30 with about 14-15 ft^3 to work with.