Depends on where you go. I use allofmp3.com (Russian). It's cheap, legal (do a Google search), and you can get varying quality all the way up to CD. I have all of my music on my iPod and it is all using the LAME coded (Alt-Preset-Standard) which is a variable bit rate (VBR) around 192 kbps. I run it through very high quality earphones (Westone UM1's) and also through my Surround Sound system. I'm not a golden eared audiophile but I'm pretty critical.
Thanks!