The 8801 supports 11.2 speaker channels. The X4000 supports having only 9.2 of them active at the same time, although all of them can be connected and calibrated individually. You have to decide which pair of surround speakers should be disabled while watching a particular movie.
The X4000 includes a few features that the older 8801 doesn't have. Most notable is the ability to send stereo PCM audio to its Zone 2 analog outputs. The 8801 requires analog connections for external device audio to go to Zone 2. It can't forward HDMI or S/PDIF input signals.
The X4000 includes a few features that the older 8801 doesn't have. Most notable is the ability to send stereo PCM audio to its Zone 2 analog outputs. The 8801 requires analog connections for external device audio to go to Zone 2. It can't forward HDMI or S/PDIF input signals.