@ChipByrd,
In your original post you say, "Over the years, I have downloaded lots of music." This makes me think you have been doing this for some time and probably have lots of 128 Kbps mp3 files (poor music quality). I haven't seen it mentioned here, so I will - are you aware of Apple's iTunes Match service? For $25/year they will scan your hard drive and provide you with 256 Kbps VBR versions ("iTunes Plus") of all the songs in your library, regardless of how you obtained them. These are available "in the cloud," but I believe you can also download them and replace the lower quality files in your library. There is a limit to the number of songs for which they'll do this - I want to say 3,300 but I'm not sure.
If you're really serious about moving into the future with high quality music you'll want to do as the previous posters mention and go with lossless formats - FLAC, ALAC - or uncompressed formats - WAV, AIFF.
