New CDP vs. older used and more expensive player

I've been thinking about buying a new Rega Apollo -- I currently have a Planet 2000 -- but I've begun to wonder about spending a bit more in favor of an older used player. I'm particularly interested in the Krell KAV-300cd, which I could pick up used for several hundred more than a new Rega. As a rule, when it comes to CDPs, is age more of a factor than in other components? Is the technology moving so fast that old is, well, old?