Well I've just started replacing my speakers today... only taken 2 years to get to it!
Imagine my surprise... after all this talk about 30W 2ohm speakers... I've removed my rears to discover I have 20W 4ohm! Component number 92158088. Mine is a 2009 MY10 SS.
I've yet to do the front, but this has pleased me considering I've bought Alpine SPS-610 (80W / 4ohm) for the rear and SPS-610C for the front. Also, the SPS-610 just slot straight in... you do have to use the spacer provided, but attach that to the plastic pod and then the speaker to the spacer... no other modifications required. I'll update once I've completed the front.
PS - thanks for the write up... it has helped a lot!
Edit: I've now completed the job... the tweeters were a bit of an issue but I found that the Alpine ones fit on top of the factory ones with some special glue and this was able to be screwed back in... it cleared the trim just.
It was interesting to see all speakers front and rear in the door were the same, and only 20W 4ohm (not 30W 2ohm as described earlier).
One of the problems I can see is the plastic sheet inside the front doors... it tends to rattle and go crazy at higher volumes so I'll invest in some matting soon. Apart from that it sounds sweet