I have been unsuccessful in finding information regarding the rear parking assist however a message is displayed on the radio when the radio is on and the car is in reverse. The message says "REAR PARKING ASSIST ACTIve" (the ve are lower case, I assume they just ran out of space.) The parking assist does operate regardless if the radio is on or off and it doesn't seem to come from the normal car speakers. I need input here, if have done a stereo in a 2005-2009 Volvo, please weigh in.

You actually bypass the factory amplifiers when you do an aftermarket radio installation. This causes you to loose the center speaker on the dashboard. The easy way is to get a simple single channel amp and run it through a pre-out on the head unit. I did this on my 2001 S60 and it cost about $60 total. Is it really worth it? No, not really. I did it because I'm a retentive perfectionist with a massive case of OCD.

This is a pain. The places that did make stuff are no longer in business or no longer make Volvo items. I checked Pac-Audio and they list a ton of steering wheel control interfaces for a 2007 Volvo XC90. I have a link at the bottom. That may be compatible with the S60 or at least MacGuiver-able to work. I need input here.

Another EPIC PITA. This requires a Volvo Dealer that knows what they are doing (which finding one, is the hardest part). It could also be costly, ranging from $50.00 - $200.00 depending on the dealer. All the Volvo systems are interconnected and when you remove the radio it starts throwing codes. The Dealer will have to do a software modification on the car and actually remove the radio.