Hi
This is an english forum so I'll reply in English.
I have to warn you with switching the mid-range speakers. B&O has this thing about using speakers with sometimes weird specifications and as with everything, it's sum of all the parts that make the whole thing sound good or bad. So changing them out all-together might not be the best solution.
Also the fact that they're no longer original will not do any favors to the value.
That being said, and having done a couple of penta's myself, I normally would refoam the surrounds with rubber (I also used the good-hifi ones). Foam is ok for the midranges as they don't give too much physical action, but you'll end up with the same thing over again in a couple of years. The rubber surrounds last longer (forever?) though they need some time to 'play in' and soften up a bit. I have don a pair of CX100's a couple of months with rubber surrounds and they needed playing for about a month to really get them going well.
IMO it's more important to update the caps in the cross-over to clear up the sound. That does really make a big improvement. Certainly so on those penta's. Also check the currents on the transfo's .
I'm in NDG close to Sherbrooke street, beween Decarie and Cavendish