[ptlvr]

Im not sure about the 2006 models but when I insatlled my Kenwood head into my 2005 model I had to by an adaptor for my Sirius Tuner,(it plugs in the cd changer port on the back of the radio).You're best bet is to go to Best Buy,Circuit City or Someplace like that and ask them what you would need.
As for the speaker ports that sounds like the stock mounts for the factory rear speakers which means the wiring should be there you just have to dig around for it,Low profile 6x9s should fit there with no modifications needed. Btw did you buy the pt new or used as it seems strange that a new pt does not have the rear speakers?