NAD C542 can't play SACDs, it decodes HDCD though.I haven't heard the others so I can't help you in that.

From what I've heard the Marantz sound signature is bright and forward while the NAD is more laid back.Also consider whether SACD playback is important to you or not.If not so, you can save money with NAD and get HDCD playback as bonus

imho, it doesnt make a diff if you are spinning CD in SACD player as the player is more meant for SACD discs itself.

You must be new to da internet.

Don't know the difference between KI Signature and without

Nolah SACD player seldom performs better than a dedicated CD player for redbook CD playback if they are within the same price range.More cost is spent on improving the redbook playback quality rather than splitting between that and SACD.

Usually the NAD C542 is compared with Cambridge Audio Azur 640C for performance and price range.Of course the sound signature is different, to me its thinner but punchier than the NAD.
Of course AV amp can be used for stereo listening but a dedicated stereo amp should do a better job at that, if you're not fussy about that and are planning to use it with video and multi channel audio then stick with AV amp.But get a good one

I don't know exactly which model was it but it was around the same price range,I did not like the Denon player so much.Azur 640C was okay but the thin sound was kind of weird for me so I picked the NAD C542, the HDCD bonus did not hurt either

I don't know exactly which model was it but it was around the same price range,I did not like the Denon player so much.Azur 640C was okay but the thin sound was kind of weird for me so I picked the NAD C542, the HDCD bonus did not hurt either