Glad you finally got one. The ebay one I got from about 2 weeks ago has not shown up yet, seller says it is on the way. I'm no hurry because I do no have the rear speakers yet.
I have not seen Peck's kit in person, just the Porsche version. On the Porsche version with there is a 4 wire extension with a female connector on the end. This extension was designed for 2003-2004 models that have a 6 channel amp as the rear speakers are hooked up to the amp, not the back of the radio. But clever 1997-2002 Boxster owners have figured out they can use that extension when they put in the 6 channel 996 amp.
You unplug the brown male connector on the back of the radio for the rear speakers, then plug this connector into the brown female connector for the 4 wire/pin extension. Then you run the 4 wires/pins into the front trunk via the large rubber gromet above the gas pedal. If you remove your battery it is easy to see this gromet.
Then you put the 4 pins on the end of the 4 wire extension into the female connector that goes to the amp. You need to first check the male connector on the 996 amp as I bet there are 2 plastic internal keys you will have to cut away, or the Boxster female amp connector will not mate with the 996 amp male connector.
Make sure you put the 4 pins in the correct location, as they are a pain to remove unless you have the correct pin removal tool. Also note that apparently the pin location on a 1997-2002 is different than a 2003-2004.
http://www.renntech.org/forums/index.php?showtopic=3389