No question separate systems are the best. Basically you have to buy two separate systems and integrate them in the same location, which forces physical space trade offs. If at all possible do two separate systems in separate locations.
surround processor?
Where to go? Older Lyngdorf MP50, JBL SDP-55,Arcam AV40.Lexicon MC ( the cheapest)? Love to watch the movies but also listened to 2 channel stereo. Are there a big sound difference in those? Just the general advice please. Will probably look into second hand.