I just installed a Sundown SAE-1000D mono amplifier, and single SA-12 subwoofer in the trunk of my F22 to add some low end response to the poor factory HK system.
Overall the install was fairly simple and quick. More so if your amp has high-level speaker inputs it makes install a snap.
The stock amplifier is in the trunk behind the left trunk mat, along with the dreaded ASD module. The headunit speaker outputs go into the ASD first, and then into the amplifier and finally to the speakers. You can't just unplug ASD to bypass it, you must actually rewire headunit directly to amplifier if you want a hard bypass. But that's another topic totally.
You can grab headunit speaker ouputs, right left (+ Br/Blu, - Br/rd) and right rear (+ Gr/Ye, - Gr, Blk) wires directly at the ASD module harness. If you need a remote turn on lead for the amp, grab it from the black wire in the ASD harness. But my amp had remote turn-on feature from just the speaker level inputs, so no additional wires were necessary. Your mileage may vary, check your amp's manual.
There are also Line output converters (LOC) or a line deferential converters if you only have RCA inputs on your amp. Both of these are good products and they give you a remote turn-on wire, which means one less factory wire to tap.
http://www.pac-audio.com/productDeta...ProductId=1188
http://axxessinterfaces.com/index.ph...products_id=18
Here are the wiring diagrams that I used from my research for this project. They are the same diagram, but the second is just a close-up on the Head-unit/ASD/Amp connectors. You'll notice the first includes all the amp/speaker connections.
Attachment 1207145
Attachment 1207146
The alternator in this car is huge @ 210amp, and the electrical system is extremely beefy to handle "extra loads". You can you wire an amplifier in the trunk with less than 3 ft of power and ground cable direct to + and - studs you can have an amp up in no time. The battery studs are 13mm nuts, be careful when using metal tools around these
The plastic cover on the positive stud pops off easy, and you don't want to hit that when your on a ground or vice-versa.
Absolutely make sure you fuse your positive amp feed as close as you can to the positive stud, and within proper ampacity of the wire. The amp has it's own fuses, your protecting the wire from shorting to ground. I used a 125 amp mini-ANL fuse for my 4 gauge wire.
Hopefully this helps somebody in the future.