I own the II+ in a headphone system made up of lcd-2 and beta22 and know every bit of its flaws.
Reading here that the pro is not that much better is telling that something must be wrong in the HRT line of dacs.
At 349$, the II+ has some serious competition. Though I cocnluded it is on par with a TerDak Chameleon I heard (550$, not that great dac), it is not as resolved as those wm8741.
YMMV, the II+ is a good unit, but not good enough for my system
It needs to be, for his lack of features, a better sounding unit.