About 10 years ago, there was a stark difference between CD players. But year after year, as DSP chips got faster and faster, the cheap players the next year sounded better than the most expensive players from the previous year.
Technology has gone beyond the point where a 44.1 KHz sampling rate is technically challenging, so most CD and DVD players sound the same. From the production side, the slower electronic components have been discontinued and the more powerful, faster DSP chips are dirt cheap.
Differences can still exist depending upon how cheap the manufacturer goes in circuit design and part tolerance and testing, but the differences aren't nearly as great as they used to be.
I say save your money for where it really makes a difference, and that's in quality speakers.