Rene,
I can't seam to tell the 990 that there is no centre speaker!
But that's a bug in the speaker configuration function. The solution is to fix the specific problem (i.e., allow the centre to be set as 'none').
End user control of centre channel steering is a useful feature when the centre is derived using steering, but it is not the solution to a speaker configuration problem.
Dolby PLII and PLIIx are matrixed into two channels, no?
PLII
x can be applied to 2-channel and 5.1/6.1-channel material.
Historically Dolby Pro Logic decoding was done in the analog domain, IIRC.
It was when Pro Logic first came out, but since 1988 that decoding has been done in the digital domain. That's 17 years ago. Other matrix decoders (PLII, PLII
x, LOGIC7, Neo:6, Circle Surround II, etc) have all been digital since introduction.