suppose I can bring my button RS-1. Not sure how it sounds compared to a 1i. It sounds pretty awful with the Sansa clip paired with the O2. Then again I've never exactly gotten the sound I want out of it no matter what I paired with it. I picked the Arcam 73 in part because it gave the RS-1 some much needed bass while also taming the treble some. That O2 will drive a K701 and DT 990 600 ohm pretty loud even out of the clip. It got the 701 louder with less volume than I needed for the DT 990. 701 sounded pretty bad out of the O2 as well. But, I think both the 701 and RS1 sounded accurate when thinking about their frequency response graphs. 701 sounds much better with the heed can amp, but I wonder if the heed has some coloration or something that is making it more pleasant. There's thing I like better about these open phones, namely the timbre, but I really prefer the Amperior over everything I own. The low impedence closed phones don't sound the same when plugged into the O2 vs being plugged into the Sansa clip by itself. More liquid, less solid sounding, spreads out horizontally a little more, blacker, cleaner background. The highs and bass seem to have more power. It can get fatiguing. I wonder if my audioquest evergreen cable is changing something. Distorting some frequency or other. I'll have to try a generic one. For the first time I'm just plugging stuff directly into the Sansa. It gets more than loud enough with the Amperior. Still adequate for the HD25-1, K550, and UE6000. I can bring the Ibasso amp. I hated the UE6000 when paired with it. Just made it dull. It seemed to give the 550 a fuller sound that I liked, but also made some albums unlistenable due to bad treble spiking. Harlan Cage-Forbidden Colors was one. I'm trying to recall the others. It's probable I made a note in a thread somewhere on here. I didn't have that horrible fatigue when using the Sansa directly or the K550 into the O2. Probably what I'll end up doing is packing the closed phones in one bag and the open in another. Throw the O2 and Ibasso P2 in there. Maybe bring the heed can amp as well.