Install thread 2009 Prius II amp and HU

The active sub that I won still hasn't arrived, so started updating the Prius...

Aftermarket 1999 headunit
Use line-input for the MP3/iPod capability of the carkit
Add speaker as the carkit no longer plays through the doorspeakers
Add 4channel amp, 2channels for the OEM fronts and 2channels bridged for a sub (fronts are OEM speakers for now and sub yet to be bought or build).

My Imageshack is pretty much full, so only a few pics. Will update when I have more pics.
Current status is that the HU is in, but doesn't work anymore so I switched to mounting the amp before I pull out the HU again.

There's ample room under the seat, so I mounted it there, but here's some pointers:
I unscrewed the 4 bolts, but didn't dare to pull out the plugs on the seat (due to possible faults in airbag/ECU). So I put the headrest on the dash so I could drill in the sliders. While I was inside the house, the seat fell back and broke my M4 threading-tool. So 2 out of the 4 threadings I had to make were made by screwing in a disposable bolt, which doesn't work well.

Two important pointers to anyone trying this:

Also, when screwing into the rails: don't let the vast amount of dust fool you like it did me: if there's dust, then the slidingmechanism obviously has room at that spot and doesn't touch the slider. WRONG. There's 1mm thick dust, yet the slidingmechanism halted on my 0.5mm extruding bolts.
With a washer, the bolts now do not stick out into the sliding-frame anymore.
Second point: there's a bulge under the front of the seat. I put the aluminium strips as far forward as posible. This eventually led to the amp coming under stress due to this bulge. Once I moved back the amp 1cm, all is well.

Here's what it looks like:

I undid the first wire-guide-hang-up-thinghy that holds the wiring for the seat as there was too much stress on it when sliding the seat all the way back (in this pic it's under the second transistor in the lower row of four.)
I also wanted to put the amp on top instead of upside-down, but the clamps that lock the seat in place after sliding it would come quite close to speaker and powerwiring, so I decided against this.
The amp btw is a Helix HXA400: 2x65Wrms and 200Wrms in my intended setup.

Still to do: wire up the amp and go find the fault in the headunit. I will be putting in the 68.1 ohm resistor (yes, 68.1 and not 68, I nicked it from work, as I only have .25W resistors (E96) and at work they have the E192 (iirc) range in .6W versions. Since there is some confusion as to the powerrequirement (0.5W or higher?), better safe than sorry).
Right now the HU is hooked up to a non-switched cig-lightersocket BEHIND the dash that the previous owner put it for his navigation-unit (and left his USB-charger plugged into adding to the always running seepage current)