I've added door speakers to both my Zeds that came with the basic speaker system, just splice them into the tweeter cables running through the door and hey presto you've got sound from the doors. Took it from sounding like any speech was coming from my feet to sounding like it was coming from around the cabin. Well worth the upgrade, think it cost me about £30 for speakers each time. If you can get them with the plugs it's easier.
Brilliant pal!!
The tweeter cables are in the right side of the door anyway so yep gonna do that!!
The 2.5i is a late 2003 and was pre-wired on one door (drivers from memory), but I had to splice the passenger door in. 3.0si needed both doors splicing in.