So I think I'm going JL FiX 82 from the H/U, then to a Helix. I like the EQ and tunability of it. Thoughts?
Run the midrange into inputs 1/2, high frequency into 3/4 and call it a day.
You will most likely need the FiX-LSA-4 load sensing adaptors. We have received word from many dealers that the amp displays high frequency noise or muting if it doesn't "detect a factory load". The FiX-LSA-4 tricks it into seeing a factory speaker.
I don't think the output of the head unit is variable and I believe it's all CAN controlled, so you will need to grab your signals after the head unit. If using the OEM steering wheel controls you will be subjected to volume dependent equalization. If you don't want that simply use a DRC-100 to control the output from the FiX, or you can control the output from what ever DSP you are planning on using. A FiX 82 optically into a TwK D8 is a pretty powerful and cost effective integration and system tuning set up!
Let me know if you have any other questions!