If you get a good enough head and good enough all around speakers, you won't even really need a full sub.
The GM head unit is extremely dated at this point. I'd advise doing a full reinstall.
If you are on a tight budget and need to go in steps, I would go
Rear speakers->Front speakers->Head unit. In that order. Bearing in mind, with a new head unit you should cut out the Bose amp and do a speaker rewire.
*Not 100% sure here*
IIRC the wiring harness from the stereo to the amp is the same as the harness in a normal system (Bose only) so it doesn't need all of the dash ripped apart, you can find where they lead to the amp and continue the signal from there.
Sent from my ASUS_Z00TD using Tapatalk
