Geoff, there's no reason to hesitate to get a combination CD/DVD player; they use a dual laser which operates at a 780nm wavelength which is optimal for CDs and also the 650nm wavelength needed for DVDs. A separate CD player has no advantage in this area. Look for the features that you want at the best price that you can find; sound quality isn't a factor. My own preference is for the megachangers such as those offered by Sony, and I would never again put up with the inconvenience of a single-disc player, but you may not have that feature at the top of your list.
