I use music also through High quality Sound systems - agreed on a Train / other public place etc with crappy headphones it doesn't make a huge amount of difference -- but do you EVER want to hear a song in better surroundings -- then the limitations of MP3 with hideous artifacts become all too obvious.
Also by storing the music in a LOSSLESS format you can copy it to whatever sort of newer device (with possibly better compression algorithms) appears.
There's no reason to suppose that a newer and better compression algorithm to replace mp3 won't appear in due course -- physics / maths always evolves.
If you start with a lossy format further transcoding will degrade the music even more (especially if the original you started with is at a low bit rate to start with).
Suggest you try a Sample track from HERE at STUDIO quality (24 Bit @192 kHZ) -- beats even CD sound which is a miserly 16 bit @ 44.1 / 48 kHZ
Of course you need some sort of player and sound card -- VLC will actually handle 24 bit 96 FLAC tracks directly if your sound card can handle it.
Otherwise just route the digital output directly into your amp as a passthru and let the amp do the D/A conversion for you.
Linn Records - The best recordings in Studio Master Download, Vinyl and SACD
Download the sample and if you've got high end audio you'll be BLOWN AWAY.
Added -- getting MP3 into flac is easy -- just google for flac transcoding -- I'm not sure this would be worth it as any transcoding of Lossy formats introduces MORE degradation and artifacts.
It's best to start with a LOSSLESS source and copy those to mp3 for players such as ipods etc.
Standard MP3 tags work just fine (I think it conforms to ID3).