I concur with pmbuko in all he says. I would add that most people would not notice much with the upsampling unless your player is more than 5 year old or soo...
You would get a more "percieved increase" of sound detail in HDCD and SACD. Some receivers even go further than upsampling and have a digital noise reduction such as in Pioneer Elites...I have yet to hear a CD in my collection to hear a gigantic difference. But as in all harware you get what you pay for ... some really low end CD players and receivers do have really cheap DACs...and you would notice a difference in sound in comparison with the higher end electronics. Based on "my experiences" stay away from electronics with Ashai Kasei AKM DACs. Stick to Burr Brown, Crystal, Wolfson, Delta Sigma and Cirrus Logic DACs.
