Question about rear speakers

[Mr. Pie]

This may sound like a silly question but... when inspecting my rear speakers I see two side-by-side mounting holes under the rear speaker covers. Is the second unused hole for the lucky people who have the premium Bose sound system? If so, would you recommend getting a matched set or just replace the two origonals and add two new matched speakers (4 total)?

I don't mind the Bose sound, but time and time again I keep saying to myself... No highs, no lows... must be Bose.

Any advice would be great.

Thanks all.

[Storm.]

In my E280 I installed another 2 speakers in the back shelf of my car as well, but i had to make sure that they ended up with the same ohms.

Also i'm looking into fitting speakers to my dash and rear doors (my car didn't come with them either)[:(!]