I'm looking to buy a new cd player and I'm leaning toward the 555ES but it doesn't have the cd upsampling I keep hearing so much about. What is cd upsampling? Does it make a huge difference? I'm simply looking for the best 5 disc cd player for 2 channel stereo, right now I have no real interest in SACD. Should I wait until someone offers a 5 disc player with it? Thanks... James ps If it matters I have a Sony DA5ES with Studio 100s. Thanks!