Mab2112, I now understand that they can not be biamped or biwired. However, John's suggestion to use resistors has made an enormous difference in the sound of these speakers. Today we started using 2 Radio Shack 1-ohm/10W resistors per side and my son and I agree that the top end is much more natural. Before, the sound sometimes was eardrum-splitting with many recordings. With the resistors, there is no apparent compromise in sound but all frequencies are much more balanced.
We ordered better (?) resistors from an online company to replace the Radio Shacks eventually. If all 2.7s suffer from this exaggerated top end (that is, unless you like the feel of blood running down your temples), this solves the problem quite nicely.
Thanks to all once again and best regards,
Santiago