I am just about to start an audio upgrade to my 3rd Saab 93 and 2nd convertible and have some questions. I think however, i should contribute first by explaining what I have done in the past that touches on this discussion:

Just gave back 2008 9.3t sedan with Bose system (changed jobs) -But...I had replaced end of dash speakers with Infinity 32.9cf's and a 42.9i for center channel. 32.9 required that I dremel the ribbing underneath the dash grills for them to fit - this worked! 42.9 made a small difference vs Bose center speaker - the 32.9's made differences similar to the Boston S35's but brighter perhaps. Front door speakers replaced with a set of 6.5" MB quarts - cant remember the model - this added some bass to the front sound stage but probably sucked some midrange out as they were 4ohms and the saab's were 2 ohm i think - ok for me as my hearing needs more treble these days! I actually cut the saab door speakers out of their frame and mounted the quarts onto the plastic frame of the old speakers so they fitted properly.. these ran directly off the Bose amp in the trunk ( boot- if you are a Brit like myself!) Researched the Bose amp and decided to keep it straightforward as the car belonged to the company i worked for... used soundgate line output converters on the subwoofer outputs and connected an old Linear Power amp at 65w/channel. Replaced 6x9 which where very wimpy with a set of Kicker CVT 65 6.5" 'subwoofers' on a fiberboard cutout - they gave a bigger kick than the originals. Disconnected the 4" fillers in the rear deck to preserve a forward soundstage. This setup sounded pretty good and a decent improvment over the nasty cheap Bose system. By keeping the H/U i preserved all the controls and it remained 'stealth' - I am 50+ so i don't need to set off car alarms with 1000w 12 inchers like my son does....

2002 SE Convertible - wifes car - just lost it in an accident (wife is fine!) JVC HU Coonected to MB Quart Discus 4 chennel amp. HU ran Boston S35 in the dash. Discus ran MBQuart FWA 160 mid-bass units in front doors. Rear speakers where some 6.5" 'subwoofers' from Pyle - they were cheap but good value compared to the Kickers in the 2008 above - don't recal major surgery to get them to fit - more than enough bass for my wife's Christian music... and didn't rattle when Mary J Blige or Peter Gabriel were doing their thing either. The Bostons didn't need high pass filters from the HU and the amp crossed over from the doors at about 250hz to the small subs in the rear - extra bass is needed in an open car so the subs were crossed quite high to help the doors - at the expense of some directionality of the bass (deep bass is not very directional so mid bass from the doors kept the sound stage forward. The Bostons in the dash sounded less 'bright' than the Infinity's in my 2008.

OK my question... We got a 2007 aero convertible yesterday for my wife - I see the 3 dash speakers and these will probably be replaced with the Infinity's from my old 2008. I might leave the doors alone for now as I swear this car has a subwoofer somewhere - sounds like it's in the dash? Same generic GM HU as my 2008 and an amp in the trunk ( boot!) no Bose branding anywhere...
So where is the subwoofer in a 2007 aero convertible and is it worth replacing? ( I have the Kicker CVT 65's in the cupboard and the old Linear Power and Quart Amp to power it/them)
What size speakers are in the rear side panels? could i fit some 6.5" there as we did with the 2002 SE?
Is this essentially a Bose system without the $800 labels on the grilles?

Thanks! Gerry