Folks with portable amp rigs, what format do you use?

I don't have as elaborate of a setup as you do, but I mainly use Apple Lossless or 256 Kbps AAC VBR. It makes a difference no matter what headphone I have used.

I run mostly OGG (q5) files and some MP3's.

When I use my rig with an amp, it's 3rd Gen Nano > stevenkelby LOD > Xin Supermini > ER-4P / UM2

I use a mixture of V0 mp3s and lossless ALAC files. That's just because most of my music is in that format though, and I'd prefer not to convert. On almost all music, high bitrate mp3s are totally transparent, especially in a portable rig. I just have lots of lossless files for archival purposes (and to a certain extent peace of mind). Certain music seems to not respond well to mp3 encoding and exhibits obvious artifacting, but otherwise you can't tell the difference. Using uncompressed wav files is just silly though.

As for your rig, the IEMs are definitely the "weak point" if there is one. I'd recommend selling them and your ludicrous LOD and getting some better earphones and a more sensible LOD. I'm even of the opinion that better IEMs sound better unamped that worse ones do amped. Do some serious A/B testing to see if the amp makes a significant enough difference to your ears to warrant lugging around, and if not, that $250 would pull its weight a lot better invested in earphones. I did that when I had SF5Ps and the difference was pretty small, certainly not worth the trouble. Even now I never use an amp when walking around, only when I'm sitting still somewhere and I want to squeeze the very last drop of excellence from my ER-4Ps.

The crazy LOD is definitely not necessary. *Maybe* if you have $1300 IEMs and a crazy amp and an iMod you could convince me that it makes a difference, but I have a cryo copper LOD and no rig I've ever had allowed me to discern a difference between it and my more generic one. That particular one is especially silly because of its size.

No, there isn't. They contain identical information.

FLAC. Avoiding ALAC after hearing significant differences between an EAC ripped FLAC with an iTunes ripped ALAC. Seems like iTunes filters "unwanted" sounds.

Lossless: FLAC
Compressed: Ogg Vorbis

Just say no to proprietary, patent-laden, encumbered formats. The above open formats also happen to sound better, too.

FLAC or 320kb, I can't tell a difference between those two on my portable rig

The ripping software is the problem there. My ALAC files are EAC ripped and sound identical to FLAC files.

i mostly use apple lossless with my ipod. i can hear some subtle differences between that and 320k, but it is not as noticeable between 320 and 128. but hey, the best thing is to just rip a couple songs you're familiar with and listen for yourself. it doesn't cost you anything.

I use proprietary KLS because I have to

Lossless for me.

ipod 80gb > Hornet M > se 530's.

ALAC, 256 and 320.

The 256 files were purchased online.

ALAC and FLAC here.

iPod 80gb > Corda 2Move > Senn HD-650

They're identical as data containers, but there's a possibility that they can sounds different if ipod's internal decoder works better with apple lossless. Theoretically.