I am looking of a set for new control arm bushes too. Because BMW has a couple of superseded versions of it, there's no easy way to work out if the non-dealer supplied part would be equivalent to the latest version. So I am going to cough up for the dealer part.
31 12 6 783 376 Current part
31 12 6 777 850 Superseded 11 May 2007
31 12 6 757 623 Superseded 16 Jan 2007
I have a 3-4 year old Mayle HD rear shock mount. It dried up and shrunk like a walnut. On the other side I have the 8 year old original factory mount that remains "rubbery" and supple. For me at least any Mayle part is off limits for my car.
For the speed bump infested roads I use, I reckon the powerflex bushes would work for me better. But I prize noise and vibration comfort over all else. So I could only look on in wonder. Also I am not sure how much extra insurance I would have to pay to declare those kind of bushes as mods.