Just a heads up that aftermarket speakers may not sound as loud as the OEM Bose speakers. The Bose radio/amp may have an non adjustable eq curve tailored to the OEM speakers.
Check the impedance (ohms) of the stock speakers. They are probably 4 or 2 ohms. If they're 2 ohms then replacing them with aftermarket speakers may result in less "loud" since most aftermarket speakers are 4 ohms. Lower ohms = more wattage from amp (generally). If they are in fact 2 ohms then you'll probably want to replace them with 2 ohm speakers, but there aren't many options out there. Off the top of my head I know that JBL makes 3 ohm speakers which would be closer.
Coaxial design would be fine. Going with a component set gives you more "tunability" and potentially more clarity, better response.
PowerBass also has 2ohm and 3ohm factory replacements. They sound pretty good as well. PowerBass OE 6.75" CoAxials
Scoop up 2 pairs, front and rear doors.
But...from personal experience, if the Bose speaker isnt messed up and playing crappy, it wont sound much better.
Bose is made, in my opinion, to sound as clear, and flat as possible. Just changing the head unit will have a DRAMATIC change. I did that in my 2008 Tahoe with Bose. All I did was put a Phoenix Automotive android big screen head unit in it and it literally sounded like I changed all the speakers, and I only changed the head unit.
The bass increased to literally shake all mirrors and the mids and highs were MUCH crisper and cleaner.
Friend has a '13 denali he changed all Bose speakers to the Focal Integration series, and its better. But not nearly as much as a head unit swap.