Clex2-
I hate to burst your bubble on this one, but that is not my car. I have just been doing research to try and figure out the configuration of the battery on the 323ti. I found that picture on another enthusiasts website:
http://isurfer.mummelnase.de/HP/Kofferraum.htm I am a US member and have a '95 318ti Club Sport like yours (at this point minus the m3 engine, but that will be changing soon!)
I looked at the ETK and it indeed shows the subwoofer for the 323ti. I attached a pic of the part info.
I made contact with a 323ti owner today who said he would take pictures of his trunk to show me the configuration of the battery. I expect to get them tomorrow or Wednesday. I can also ask him if he has the subwoofer installed.