Is there a difference in sound quality when streaming TIDAL Vs CD player

I hard wired my modem located in my family room using Cad6 cable to my Apple TV and direct wired my Apple TV to my ARCAM AVR550.  I have an OPPO 203 connected by both an RCA cable and by HDMI to my ARCAM.  

The dealer I purchased my ARCAM from told me to play my CD’s through my RCA connection and to watch DVD’s through HDMI.  If I listen to CD’s through the RCA, aren’t I using the DAC on the OPPO player rather than the DAC on my ARCAM and wouldn’t the DAC on my ARCAM be a better DAC.  My friend told me I should use a digital cable rather than an RCA to improve sound quality to utilize the DAC on my ARCAM?  If this is the case, wouldn’t the HDMI be the same as by using a specific digital cable?  I listened to my CD’s through the RCA Vs the RCA cable and I thought it sounded better through my HDMI cable.

i will be looking forward to your responses.

Thank you,
I find CD to be deeply flawed medium and much prefer Tidal, my reference is my turntable and live acoustic music. 
I can hardly tell difference between CD and Tidal. I am now subscribe Qobuz Studio (a lot 192kHz/24bit and 96kHz/24bit), I am quite satisfied.
I just read a review on the Legacy Focus speakers.  They must be incredible.  I wonder how they sound compared to Jim Salk's Song3 Encore towers priced at $6,000.  To date I have not heard better.  I couldn't believe how they sounded compared to a pair of $60,000 speakers I hear at the RMAF in October.  I don't think anyone handles the Legacy Focus speakers in Denver, but I will be looking.

To change the subject, I wonder how people in this group feel about how important amperage/current is when buying an amplifier to create superior sound quality?  For example, Parasound has a 5 channel amplifier that delivers 180 watts and 67 amps per channel while Primare has a 5 channel amp delivers 150 watts and only 30 amps per channel.  I contacted Primare and the guy told me sound quality is not dependent on current.  He also told me the Primare would blow away the Parasound amp.  I think this guy was blowing smoke and mirrors.  I wonder what people in this group think.  This in itself would make for an interesting discussion.
Someone just replied and said he thought the sound of TIDAL was better than a CD.  Glad I am not the only one who feels TIDAL quality is better.  I hard wired my router to my Apple TV and perhaps that makes a difference.  The same person told me prefers vinyl over everything.  I don't know how this is possible because there is more noise with vinyl and the needle is only able to make contact with so much area on the groove of the vinyl record.  This said, you must be losing a lot of information and as a result detail.