I've had the MiniBox amp card for 2 weeks, played TH900, T5p and even the HD800 with the combo, sound really great with the first two, and even HD800 sounds pretty nice with the MiniBox amp card. I haven't even bothered to use my desktop setup in the two weeks because I really enjoy using HM901.
I know Dr Fang didn't suggest to use MiniBox with IEMs like K3003, but I gave it a try anyway a couple of days ago. Oh man, how I regretted that I didn't try the combo earlier. The sound was much fuller, bass and mids are quite a bit better (IMO) than w/ the IEM card, highs are very well controlled too. Never thought that K3003 could sound so nice w/ a portable setup, that's after I've tried AK120, X3, HM901 w/ different amp cards. Now I think I found the ultimate amp card for my use, the MiniBox card. It's capable of driving full sized cans like TH900 and T5p, and it works great with sensitive IEMs like K3003.
You know what, I've sold my IEM card after I tried the MiniBox w/ my K3003. Don't see I'd ever use it again anyway.