Same here (original 225s) and I have to admit that my favorite open cans are slightly bloated and the mids are too forward... It pretty much took the Mojo to come to this conclusion...
I have one, never considered using it with my phone, most likely because like Chord, I assumed that it would not bring much. But what the heck, I'll give it a go I do use it with my Notebooks for the reason you noted.
No, just the opposite, I'm afraid The Mojo revealed the weaknesses of the 225. With my older DAC (Headroom Bithead) and even with the AQ Dragonfly, it was not evident (to me) but with the Mojo it is.
Yes, Rob tested the Jitterbug with the DAVE and it did make a minor improvement in SQ when he used his laptop plugged in to the wall. With the laptop running on battery power he did not hear a difference with or without the Jitterbug. So it will depend on how noisy your source is. In the end though he did emphasize it was a minor difference. Edit: Yeah, this was already stated. Apologies.
Awesome, T4S I typically have my Notebooks plugged in (mains / AC) and run Jitterbug->USB interconnect->Mojo.
Was very close to getting Ether C to pair up with Mojo but got HD800 instead. Should arrive within 3 days. Will leave impression! Happy listening