Portable DAC compatible w/ iPhone or iPod

I've been using Oppo-HA2 with Shure SE846 and iPhone and extremely happy with it. 

Hi Folks, interesting thread.  I already own a NuForce ido.  For those folks who are connecting their NuFuorce to external DACs, can you specify which ones you're using and why you prefer them to the built-in DAC on the NuForce?  Thanks in advance to everyone who responds.

I use the Fostex HP-P1. Primarily I just use it for a transport to send to various other DACs. I'm reasonably happy with it.

Thanks - JI35: I know about the Pono player, I'm thinking of that other company that makes clever little "Toblerone candy" shaped mini DAC's similar to the Pono. I'll have to research it some more. The company name was an acronym for something...dang... it eludes me right now.

My goal is to be able to loan my little device to the spin instructor and let them plug their phone into it just to see if the power chords and the climactic moments don't have more drama to them. And the thin-ness and the harshness, hopefully some of that can go away.

Timrhu: I did not know about the Nuforce Icon ido. It appears to be out of production. I did find several on eBay for under $100 which is encouraging. One question though: does it use the mini jack from the iPod to import the raw data or does it keep the crappy internal dac from the iPod in the playback? I have a really nice sounding Wadia 171i with a digital coax out to my Bryston DAC that sounds quite nice for most recordings except all but the lowest quality mp3's. But that set up is for my home system and is not portable at all. The Nuforce sounds promising because it appears to just require a place to plug in a wall wart and a place to plug in the RCA interconnects and that is about it.

Check out the new portable batterey powered usb dac/headphone amp called Shift from Peachtree Audio. Might just be what your looking for.