To OP: tons of amps are available but with the electrical support you have, no matter what you have you will only be able to see so much power.It takes power to make power.
Id suggest you clamp your Z1a, see what power your really getting out of it. See what your impedance rise is, and see what adjustments you can make to get more power. You have a great amp and honestly thats about all youd ever need for a nice loud daily system.
My chevette has 36, it minimizes resistance. Allows for no strain when transferring power from front to back. Not saying it necessary, but if you are a hardcore competitor its worth the extra little gain.