If 2-channel audio is your main priority, then your Option #1 is most likely the best solution. There isn't going to be any HT Processor that is going to sound quite like your Luxman C-900u preamp. You could go with your other options, but like you said, 2-channel audio is going to be severely compromised, especially if you are using the subs to "add bass octaves" to the natural bass of the Focal Sopra. Everyone who runs a "hybrid rig" is compromising in the 5.1 HT side of things, but that's a necessary evil.
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If you did replace the amps, I would be very careful about matching. Your Luxman amp is likely a very good match, along with amps such as Pass Labs (especially the XA series), maybe Parasound JC1 with high-bias Class A setting.
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For processors, I'm partial to Krell S1200U because of the Class A analog stages, but it is discontinued and does not support the new features, such as 4K video, HDR, Atmos, etc. There are others, but for home theater movie excitement, probably the Krell Foundation is the best way to go.
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If you did replace the amps, I would be very careful about matching. Your Luxman amp is likely a very good match, along with amps such as Pass Labs (especially the XA series), maybe Parasound JC1 with high-bias Class A setting.
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For processors, I'm partial to Krell S1200U because of the Class A analog stages, but it is discontinued and does not support the new features, such as 4K video, HDR, Atmos, etc. There are others, but for home theater movie excitement, probably the Krell Foundation is the best way to go.