@ puzio: I agree with a BUT: It's not easy to come up with a method that works well on many pieces of music. I still appreciate that ursamtl shared his method, which allows us others to learn.
Ambisonics / AmbioPhonics is truely exceptional and hard to beat
Just to repeat that Ambisonic's goal is not to bring the orchestra into your living room, but bring you into the concert hall, so no need to look or search for single instruments coming from defined speakers.
For non-Ambisonics, I recently posted
LCR Upmix Bidules. Amongsts these is the Gerzon LCR, but the others are also worth checking
as they produce some reasonable LCR from LR.
Regards,
Andreas