[WC]

It depends on the receiver. My Marantz SR-6005 AVR has the ability to use 4 amp channels of my 7 available channels to biamp the front speakers. The other 3 channels are for the center and surrounds. Since they all use the same power supply, I would guess that this is not strictly vertical or Horizontal biamping.

[celo]

Thanks! So, what I understand is that even though the receiver is able to biamp, since it shares the same PSU, it is not a biamp that will give real advantage.

You need to use two identical (preferably identical), stereo amps to have the advantage (subjective but at least technically it has an advantage). Yes?