A small update:
After the second replacement of the product, KC2 still has not been able to work normally. At least with SATA HDDs and DVDRWs I have had.
Recently, I bought a 640GB SATA HDD (Western Digital
WD6400AAKS) and got my DVDRW replaced (LG H55N).
Guess what!
It "works" (!) but.. I cannot use speeds for burning higher than 8, or else burning fails.
If I select 8 speed burning, everything is fine, no problem occurs.
If I select 12 and more, the burning process goes fine to 25 percent, then, when the drive increases the burning speed, drive buffer state changes rapidly from FULL to BLANK and the drive's led blinks just from time to time, as if it wouldn't have enough power to continue @ higher speed.
Well, at least it works a little bit, no DMA - CRC errors occur, only this weird behaviour if burning speed is set to 12 or more. (in test burning too)