It's not technically a problem to use Concero HP via 1/4" to RCA adapter. Set volume to appropriate levels and it sounds great, though it does lose out to Concero HD in two areas.
First, aesthetically. It just doesn't look as neat and orderly with a cable going from the headphone jack to... wherever else it might need to go. Best to keep that stuff all around back, which Concero HD does.
Second, it takes a penalty in the form of SNR and other specs. Not a massive penalty, but it's there. And to my ears it is noticeable if not a deal breaker. I used Concero HP for a month in my desktop rig with Adam Audio active monitors and it did a very credible job, so it's not like you can't enjoy the experience. BUT - for dedicated DAC duties I do recommend the HD instead. So you gotta examine your usage needs and go from there.
Compared to Hugo, the Concero HP and HD don't fall that far behind. Hugo does have superior detail retrieval and an overall "larger", more believable sound. The delta is not huge though. I think if you never intend to use Hugo as a portable, and you don't need all the extra input/output options, the Concero models are likely a better choice for most people. I do love Hugo for SQ but the ergonomics frustrate me to no end.