ProtegeManiac
Headphoneus Supremus
I quit on mp3 10 years ago. FLAC is it. The only question is, have you started down the path of Hi-Res FLAC files? One of my friends won't listen to anything but Hi-Res. However, until they get more music recorded in Hi-Res format, I'll stick with Redbook FLAC and listen to Hi-Res when I can get it.
Yes, there is a difference - especially as your equipment gets better. Better equipment, the easier it is to tell a difference. I'm not so sold on the differences between Redbook and Hi-Res, though. All things being equal, a hi-res file - if recorded that way - sounds a bit cleaner and more airy than Redbook. However, there's a world of quality range with just Redbook. Some recordings are at a bit rate very close to 24-88, some are closer to a high-bit-rate mp3. A very high-quality Redbook recording is very, very difficult to distinguish from a Hi-Res, while the reverse is also true: a very poor Redbook is indistinguishable from a high-bit-rate mp3. The mastering really does make a difference.
I think that's why you'll find so many arguments claiming high-bit mp3 is just as good as Redbook, which is just as good as Hi-Res. It all depends on what you're listening to and how it was recorded.
I think sticking with FLAC at a minimum Redbook quality, then augmenting your collection with Hi-Res (when you can get it in an artist you want) is the best way to go.
DSD? I'm not that experienced in it, but what I've heard natively doesn't impress me anymore than PCM. BTW, unless you are listening with a native-DSD DAC, it's converting it into PCM anyway. If you can't tell any difference, it's not surprising.
At some point it will not be about difference but availability. Some music are only available as slightly compressed Spotify Premium, MQA Tidal, 24/96 FLAC masters from HDTracks etc, and CD. Meaning the only way to get Redbook is either you're using Spotify or you still have a CD drive somewhere to rip a disc. Given a live in a country where I'd have to import good CDs, unless it's an important enough album for me to have a physical copy of, I'd probably just download the 24/96 from HDTracks.
Not really a problem anymore since there's a reason why they're not offering Redbook FLAC on newer releases: even smartphones can read 24/96 now. You'd have to still be using an older DAC (which might not even have USB input) or CDP to even have to use 16/44.1 lossless or CD.