OK boys I did some digging - Good news!!!
The mystery rear door midranges are 65mm so just about 2.5" - They are the SAME part number whether you have DSP or regular "Hifi" - and they are the SAME speaker used in the rear panel of the E46 coupe - and guess what, those speaker sets are still available from BSW -
I already have an email out to see if they sell those 65mm midranges separately, if so, even at another $100, might be worth it to have the proper fitting and proper sounding speaker in that rear door panel.
So far my investment is $35 for the Memphis Dash Midranges, and anticipating $140 for the C2-600 component set (2 midbasses and 2 tweeters) and either buy a second set or 2 more midbasses separate.
My goal is to keep it under $300 to upgrade all speakers -
2003 X5 3.0i 5-Speed - Born on 9/18/2003
93k miles -Topaz Blue/Schwarz/Titan Int. Trim/EHCII/Sport
OEM+ with plenty of Lighting Mods
Proud 3-Pedal owner, UUC/AFE/4.8iS Exhaust/Sharked
2013 X5 35D (CEO's) - Born on 5/17/2013 -
42k miles - Alpine White/Cinnamon Brown/Premium Pkg, Sport Activity/Premium Pkg and Sound/20" Style 214/Running Boards