Logitech Z-5400 Sub repair

Help!

I've a set of logitech z5400 and last night the sub made a strange noise before kinda dying.
it now makes a very faint hum, rather than the heavy rumble its supposed to.

if you know the logitech set im talking about then you know that the sub houses the amp also, with a small "control center" running on a serial cable to whereever is handiest. becuase of this i cant just replace the sub with a generic as it means replacing the whole system and im not sure if its possible to buy one separately.

could anyone recommend someone, preferably near D13, who mihgt be able to repair this?

Its out of warranty, but ill be calling logitech after 9am to see if they can recommend someone or do a chargeable repair