DAC/ Sound card

Since I have begun the quest for accurate monitoring. I have learned much. Why didn't music retailers know about cables????
Anyway. It seems that my old Yamaha CD Player sounds more pleasant than the outputs of my Delta1010 Interface. Is it possible or likely or is it me?
Would I benefit from using spdif out and an ART DIO?
Is there a range in spdif quality with different cards. If I was going to use an external converter I would probably swap to RME Card because of hard/software stability.
Most of this curiosity has come since I began trying dozens of current and vintage amp/loudspeaker combinations.
BTW:Audiophile and HIFI Equipment Blows away the Consumer level Studio monitors. My opinion based on others and own experience.
Thanks for help