I have a Sparko Aries and firstly I should say that Alex and Dennis from Burson, Chris from Audeze and Andrew Sparks from Sparko are all great to deal with.
What I can say is that based on my listening, subjectively the Sparko Aries is as least as good as my Burson Conductor 3X ref driving my Audeze LCD4s and LCD xc. But that comparison so far has only been with 2 different DACs so the comparison is Burson conductor using its own internal DAC vs Sparko Aries with a Chord Qutest. So its not just a headamp comparison.
I might at some time get my act together and just compare the Amp stages. I could drive both the Aries and Conductor with the Chord Qutest (which is outstanding) and I think I can drive the Aries with the Burson Conductor DAC and compare it that way. I could also run both headamps with my Cambridge Audio 840C and my circa 1990 Marantz CD80, which was modded a decade ago with burson opamps, burson low jitter digital clock, new caps and a Philips TDA1541A S1 double crown d/a converter. Actually it might have been a Philips TDA1541A S2 double crown d/a converter.
The CA 840C has a fully balanced layout, twin Analog Devices AD1955 24 bit DACs, true balanced XLR outs, use of DSP processing to up-convert the signal to 24bit/384kHz. It extracts detail amazingly well and has a great soundstage. I've thought about modding it with Sparko and Burson components but hasn't happened yet. review here:
https://www.dagogo.com/cambridge-audio-azur-840c-cd-player-review/
Re comparison the problem is whenever I plug the headphones into either combination it sounds so good I just start giggling like a school kid and enjoy.
As an aside, the 30yo CD80 wipes the floor with most other players/dacs I have compared it with. Especially with simple acoustic music. And the error correction is astonishing, It played the worst scratched discs. The Marantz CD80 player and PM80 amp, which does 20 watts class A and is switchable to 100w class AB, is running a pair of Dynaudio Image 1s on the desk of my home office. The CD80/PM80 also have sensational headphone stages that runs my headphones well, even difficult loads like the LCD4s. This Marantz/dynaudio setup I got when I was selling HIFI part time when I was at Uni. Buy quality and it lasts.
The Conductor is fully balanced, and the Aries is single ended.
The Burson is sensational for music and AV, as both a headamp and preamp. Actually when I bought it the main reason was I had no headphone output in my main system and I thought I was just going to use it as a headamp and possibly DAC, and stick with my current preamp, a Musical Fidelity Nuvista, #176 of 500 made.
I never thought I'd upgrade the Nuvista, it could be the most beautiful thing I have owned in form and function. It sounds unbelievable and is the only piece of audio equipment I've ever had with valves. But the Burson is better to my ears so I'll be selling the Nuvista.
Subjective reviews here
https://hometheaterreview.com/musical-fidelity-nu-vista-preamp-reviewed/
and here
http://www.audioreview.com/product/...s is better than,the lack of balanced outputs
Regarding the Aries, this review combines subjective thoughts and objective measurements:
https://soundnews.net/amplifiers/headphone-amps/sparkos-labs-aries-review/
Even if the Aries came up better in a listening test It will stay in my home office. It doesn't have a remote, Bluetooth, wifi etc. Which doesn't matter on my desk, but would be a pain in my main system.