Hey Reddog,
Just to let you know, I'm thoroughly delighted with my Cayin C5 for portable Alpha Prime listening. Using High Gain I can't listen past 4.5-5 on volume its pretty loud. There is a lovely openness to the sound, and actually going back to my NFB-15 although the sound with a desktop amp is superior, I'm now finding that I prefer the slightly more sparkly sound that my Fiio X5-Cayin C5 combo has. So, I'm thinking of selling my 10 week old Mad Dogs and NFB-15, with a view to using the money to get a slightly warmer desktop setup. I feel maybe the nfb-15-alpha prime combo is a touch too dark. Whereas my aKG K550s just killed my ears after 10 mins even without any amping,
I can not take my APs on holiday with me using X5 & C5 its an awesome portable setup. Recommended.
Best rgds