question about 2nd gen stereos of different vintages

Question for you stereo knowledgeable folks: On the back of a 09-11 stereo, I see a blue plug. who can tell me what it is for?

I have a 2005, and the 05-08 stereo (non JBL version from trd sport, with 6 disc changer), doesn't have this plug. Not sure what it is for. Circled in blue in the photo. Question is whether I can put the later radio in the earlier truck without issue. My radio is starting to glitch and give errors. I'd like to put in another similar one, not mess with an aftermarket unit and any harnesses/adapters/splicing/install kits that might require.

Also, the red circle, I think is for an aux plug setup, like a bluetooth or aux module, etc. Am I correct in that thinking?



One final question: If one was to hook up a small powered subwoofer to a non JBL system, what is the best way to do it? Not like the factory stereo has pre-amp outs or anything. Can I just splice into the wiring going to a door speaker, and run that to the amp input? I don't think that would throw much off in the way of load, the inputs to an amp are high impedance...

Thanks in advance.

 

The red one is connector R9, used for SDARS (Satellite Digital Audio Receiver Service)
The blue one is for the satellite antenna (shark fin up on the roof)
For connecting a subwoofer, I'd use a quality line out converter

 

Thanks!