I used to work as a student sound engineer at my uni - we had a very nice sound system, but it'll set you back about £20k if you want to replicate it.
Going to gradually start replacing as much of my music as possible with LPs, but they're a huge disadvantage for travelling. At the moment even my iPod is broken, so I'm stuck listening to most music over my laptop's low quality sound card. Certainly a lot more convenient when my iPod was still alive, but mostly I'm still stuck using MP3 for digital anyway. Sourcing higher quality versions for 60GB of MP3's is a challenge. :lol:
For digital - mostly buying new music as AAC at the moment. Most places I'm buying from give me several options, and will let me download the files again in a different format anyway. Using earphones rather than headphones - again, as I would usually have my iPod to travel with - but will eventually upgrade. I have some reasonable creative earphones - they're cheap, but pretty good for the price I buy them at. Reluctant to spend much more on earphones as they tend to be rather fragile and don't survive too long with me walking around with them so much.
Not sure what the quality is like for brands for home playback - I can quote you a decent set-up for a large venue or arena though. :lol:
@James - you mentioned buying high quality speaker cables, have you noticed much difference across speaker cables for a personal sound system? Even the cheap industry cables will give you roughly the same sound quality as more expensive branded ones. What types of cables do home stereo systems use? Just bare ends?
If you're after the best sound quality, the problem with speakers over headphones is that you need to be very precise with the set-up - specific placement of speakers etc. Doing it wrong will degrade the quality, but I doubt it's noticeable in a home set-up. Headphones are also a cheaper option for getting the same sound quality, but people like what they like.