Rotel RSX 1550 vs RSX 1562


Hi I have a Rotel RSX 1550 which is connected to Vandersteen 2CE Sigs in the front, Vandersteen VCC center, Vandersteen 2CI’s as rears, and two martin logan 10 inch subwoofers. I recently found someone selling a Rotel RSX 1562 for $200 on CL. At least to my ears the Rotel/Vandersteen combo sounds amazing for music and movies. My questions are as follows:
1.) Does it make sense to upgrade? I think there’s a good chance I could sell my 1550 for more than $200
2.) What’s the real difference between D and A/B - I guess my question is does the 1562 sounds any worse or better?
3.) For video I’m running the HDMI directly to my TV and using a 4K 60Hz HDR 1x2 HDMI 2.0 splitter, which sends HDMI audio to my Rotel as I wanted 4K on my TV. As a result I don’ t think the HMDI 1.4 does anything for me.
4.) In terms of codecs or sounds formats (DTS, etc) does the 1562 offer anything extra?
Thanks,
Mike
128x128mzwerner