Just a note to try to help clarify. Back to one of the original questions, ALL regular CDs use a sample rate of 44.1 khz, and a 16 bit word length (as originally specified in the Philips/Sony Red Book). This has not and will not change for regular CDs. Although adding no new information, upsampling increases the sample rate and the word length which adds dither, raising the frequency of the noise and distortion content. Certain theories state (when the ears are not used) that this should not improve the sound quality, but by all accounts (when only the ears are engaged) it does, and by a none-too-subtle margin. I think Sam Tellig (in his own blunt, penny-pinching manner) presents a good, down to earth summary of the process in the February issue of Stereophile. Not to put words in his mouth, but his basic opinion (if you don't want to purchase the issue) is that it is much superior to regular CD without upsampling, even if not to the level of SACD, which by the way he does not think will survive the format war. I know Sam did a great job, because I know I want to buy a DAC with upsampling (poor gullible me!!).
