It depends on the format you select and the encoder you use. For the most part, 128kbps MP3s encoded in iTunes with error correction and VBR enabled will give you an identical-sounding music file. Use 192 or 256kbps if you're really worried, but music encoding routines have come so far from where they were 5 years ago that it a 128kbps mp3 created today sounds better than a 384kbps file created a couple of years ago.
10-4. Thank you, I'll give it a try.