But I’m using my processor strictly for watching movies (4k UHD & bluray disc playbacks). I don’t use it for listening to stereo music. This is in my dedicated HT room. I have a separate dedicated two-channel setup and system in a separate two-channel listening room that consist of completely different gears.
So, I can only tell you how the Lyngdorf MP-50 performs for surround movies or HT. I have previously demoed the Lyngdorf MP-50 in a different HT setup and system before buying it. It was spectacular. With Room Perfect engaged and when properly calibrated it crushed the Classe SSP 800 for HT. I never tried the Lyngdorf MP-50 for stereo music playbacks though. I also only used my SSP 800 for HT, but I have tried the SSP 800 for stereo music playbacks before and it was great especially coming from an AV preamp processor.
The Lyngdorf MP-50 does not have stereo analog audio inputs, only digital inputs. This unit is purposedly built for HT. It only has XLR balanced analog audio outs, no single-ended outs.
You should definitely get the Lyngdorf MP-50. You can use its internal DAC for your stereo music playbacks. It has USB, HDMI, AES/EBU, spdif coaxial digital, Toslink optical digital inputs. This will be a major upgrade from your Marantz AV7704.
The Classe Sigma SSP is excellent for stereo music playbacks especially when using its USB input and especially considering its asking price but the Lyngdorf MP-50 is way better for HT or surrounds especially with its Room Perfect.