Presently, I'm using A+ mainly with my NOS1704, as the up-sampling makes the DAC sound almost as good as the Hugo.
Amarra 3 I use with the Hugo. While A+ is subtly more "clear" souding, Amarra has a subtly wider, more relaxed presentation. It still bugs the crap out of me that if I edit the Amarra playlist in any way the music pauses. It is one of the worst-designed pieces of software I've ever encountered -- it is as if the people who code it don't know what threading is.
Actually I think mine is resource related. I did have Macscan running at a few Java apps running at that time.
I killed MacScan, play an album & let it run through over dinner & it actually completed the whole album with no hang ups.
Funny as I have 16GB RAM, 200GB free space, loads of swap, & I'm not running anything intensive at that time - Chrome, some Java stuff, e-mail, MacScan, A+
MacScan is a waste of time.