I would say that a moderately priced CD player will outplay a cheap DVD/CD player, because converting that digital info to analog audio is not equivalent on all machines. This does not mean that you need to buy a Krell or Classe. I found a huge difference between my old DVD player and the Onix CD-5 both connected to the same amp, speakers, etc. at same volume. My wife guessed the Onix correctly 5 times out of 5. Hardly scientific, but my ears don't lie to me.
It is more in amps and preamps, where, to me at least, the differences are negligible if the output power and its quality is the same. BTW Seth, that's the correct spelling of the word.