Thanks.
Stereo is all done now. Bass knob on the factory blank plate by the arm rest, amp hidden under the seat using a factory cover and Uber Stealth Audio light weight plywood box housing the 8" Helix sub in the trunk. Clean simple and all hidden.
This setup sounds killer. I mostly listen to rock, metal and 80s metal but tried some dubstep just to test the extremes and my rear view mirror and side view mirrors shake to the point that they become a blur. I'd say it has WAY more bass than I'll ever need. No distortion from the sub at all, no odd noises from it hitting the factory carpet over it...since it doesn't hit thanks to Nik's built in recess for it. No rattles heard inside or outside the car either. I'm real happy with it. The amp and sub pair worked out perfect since the sub is a dual voice coil (2ohm per coil which I wired to 1ohm mono) that can handle 300w max 200w RMS and the amp puts out 300w at 1ohm. After tweaking I only have the amp turned up about half way and it's perfect.
I do still wish the factory door speakers put out a bit more low end though. Perhaps I'll look into an upgrade to the stock amp and or speakers down the road to help that. For right now I'm very glad I added the sub the stock setup is seriously lacking bump!