Seat spec question

[chrisx666]

A 5 series thread now running got onto the topic of seats, not wanting to hijack I'll ask here.

My E46 325SE gave me back pain (Std 'flat' SE leather seats). I had never had any problems with any other car seat ever, and thought it was just me (until I read the other thread). I'm looking round for a change and am concerned another BMW will give the same grief - is there any particular seat spec I should look for (or avoid) in a 04->06 5 Sport or 645ci?

Thanks for any help, a test drive is not the same as a weeks commuting..

Cheers,
Chris.