The OPPO 205 has a digital coax out and your Krell Foundation 4K has digital coax in, are you running it that way? If not definitely give it a try. Not to take away from OPPO but they are not very musical IMHO, blu-ray players were designed for video. I prefer a designated CDP.
Best CDs
I'm new to Audiogon, and know the depth and breadth of the knowledge and experience of the people who post on the Forum, so I apologize for this amateur question. I'm strictly digital. I've just upgraded my system with an OPPO 205, Krell Theater 7WD, Krell Foundation 4K, and B & W 804s, 805s, and center speaker. I've played some CDs (old collection), and they sound awful. Is there a good brand or brands of CD and/or source that I can rely on for future purchases, or is it more complicated than that.