If possible, I would think ideal would be that there is master for the purpose.
If you are putting stuff online, I would assume most people feel it would suck to be appear quiet and tinny compared to all the other stuff there.
BUT, for CD, that is listened as stand alone album, not just whatever random internet browsing, it would be great if artists and labels would get back to reasonable levels of sound. I think it has been talked before, but I can only talk of gut feeling that ability to crank a bit volume from amplifier gives speakers better sound. Compared to CD you merely can open volume knob and its already full blast.
So, doing master specially for format, and further more, "CD" and "digital" ain't the same format really. CD is digital, but it ain't used in same ways as the streamed files.