Very helpful, thanks.
for the amp and sub, i know a few years back when i was doing systems on a regular. for people that wanted to keep their stock stereo and just and an amp and sub for some bass. we used a simple LLC (line level conveter) and tapped an exsisting speaker wire for the signal and then hooked up the amp and sub accordingly to that.
i havent looked in the last maybe 2 years so not sure if they have anything new out that is recommended over the LLC. but here is a sample of what im talking about
PAC SNI-35 (sni35) - Line-Out Converters - Sonic Electronix
that will send the signal to your amp to play thru the sub. but you still need to link up the remote wire, 12v power and ground for the amp.
The signal from the head unit is a pre-amplified signal in the 2007, so you do not require a LOC. You will probably have to do some twin lead to RCA handiwork, and then you can plug straight into the Amp(s). I decided to put a 360.1 LOC from Rockford Fosgate to contol EQ and output to speakers from a PDA, wirelessly (Techie alert).
If the 2009 has the same Bose system, it's likely to have similar wiring.