I have the Allo Boss v1.2 and an (original) IQAudio DAC+ and to be honest find little to choose between the two - apart from the BOSS costing twice as much
At the moment I am using the IQAudio as main player but solely because it has a very decent headphone output I can use of an evening.
The Boss is languishing in the shed system ....
To be fair I haven't gone in for all the multi-linear-PSU palaver or the isolator - one of the reasons I first got the RPi set-up was that it was good quality sound, versatile .... and cheap