That is surprising about the MCC as it is better than the R03. All the R03 media you have comes from Ritek. They manufacture and sell to others for distribution. I have some experience with R03 and I find that the quality is variable but not such that it is unplayable. Older R03 was so bad that it had to be recorded at 4X and often was sold this way even though it was originally 8X media. Liteons like +R media better than -R so you are starting out correctly, but my 812S often would burn poorly and then would burn well with R03. You should check your burns with Kprobe; this will also tell you your media code as will CDSpeed.
This will help you find a media you like you can stick with. It is also possible that your Denver player is picky about +R media. Make sure you bitset it to ROM for the best compatibility, especially when you get a new one.
Also, if you find the Kprobe scans are bad, you can lower the burn speed on the remaining discs you have to 4X. This should lower the errors and increase the playback.