I'm the second owner to get the SoundsGood system. I activated the front door tweeters and added a 10" subwoofer similar to 9-Volt (which I listened to at Electrafest). I'm actually going back on Saturday to get the rear shelf speakers activated and system retuned. Since picking up the car from SoundsGood, I have since sound deadened the rear shelf as well as the door skins and whatever else I could that was rattling from the new subwoofer. Overall I'm pleased with the sound and quality of the system. I've done some work on my car myself and was able to see their work as well and I must say that their quality for installation is top notch. They didn't cut corners, they used tesa tape wherever possible, all connections are soldered. End of the day, it's more $ than RPM but you get what you pay for.
PS, amp signal is off of VCLEFT. I believe they grabbed the 12v power for the amp from under the rear seats rather than the battery in the frunk.