W203 C32 BOSE Rear sub/ Amp options

[elite_504]

Hey folks, the BOSE system on my C32 has always sounded a little tinny. Bass is to the max on the COMAND head unit (which went in for refurb today to get the nav working again, and comand-online.co.uk, I shall report on that later!), and the speaker is responding (I assume it wouldn't if the AMP is shot?) but with barely any vigour.
Has anyone done a drop in swap for the amp, or have any fault-finding advice for the amp itself?
All info appreciated