Bose is almost pointless, just gives you a sub, don't get hung up on Bose.
Sports Chrono, for those who say it's pointless on a manual, it really really really isn't. It's great for when you want to push along and makes it much more responsive to the throttle response etc.
For me the key is why do you want a C4S? Have you driven both C4S and C2S? When I took a C4S out it was noticeably heavier and less chuckable.
My car has:
Sports Chrono
Manual
C2S
PSE (always on, just fabulous!)
Hard Back sports seats (very nice indeed)
Heated Seats (for the wife, its a cabrio)
top tinted windscreen
Parking sensor
I have upgraded the PCM2.1 as it is amusingly awful, and by that I mean unuseable even when you add an ipod connection.
Key is condition, FSH by an OPC or a good specialist is essential. If the owner talks about having changed the oil every year, not 2, or warming up the car before thashing it, then you are on the right track.
I did have an OPC warranty, but just got rid of that as they wouldn't extend because I've changed the stereo. Nice to have, not essential.
As others say, work out what you want and be prepared to change the list. Waiting for that 'unicorn' car (i like that) is madness. Prices are climbing, get on with it! Some great dealers out there, and some awful ones, so come and get us to run the rule over any car you like!