Pose,

Nice people at Logitech indeed.

About adding speakers of the "old" one to the new one, it's not really that simple.
If memory serves well, if you connect, say 2 times an 8 Ohms speaker together in parallel, that would make it zero, and in series 16 Ohms.
The first will burn your amp and the series option will half the available volume.

Every system is balanced against each other in means of speaker impedance, load and the amp being used. Changing any of these will almost every time make the sound as a whole worse.

Since you're free to explore, just open it up and with some luck, it;s only a broken wire or bad connection due to some vibrations.

Good luck,
John

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Have a nice day