I did try a lower level SPL headphone amplifier. It certainly was a solid piece, and much better than most other headphone amps I have tried. However it was definitely not on par with the Bryston, SimAudio, and the Woo. Of course they might be doing something much different in their higher models, although they claim that their lower models perform on par with their higher models. Of course it did not have most of the extra features of this SPL model. I am only referring to sound performance and not features.
I can only speak for the SPL 2730B as that’s the only one I have spent time with. I had at least a dozen other amps come through to compare with, WOO, Audeze, Bryston, various Schiit, Violectric V281, tubes, SS, Class A…
Played with about a dozen headphones such as Focal Utopia and Clear, various Sennheisers, Audeze, ZMF, E-MU, Fostex, etc…
The SPL 2370B was a professional grade instrument for recording studios, not a hobby grade headphone amp. It easily won the shootouts between itself and most other amps. Solid foundation of iron fisted grip down low with any headphone, dense and rich midrange that stood out against the more fragile and leaner sounding lesser contenders. The rich presentation did not come at the price of the amp sounding dark nor lacking any air or sparkle. It just sounded effortless and powerful. Music/recording quality always made the biggest impact rather than any flavor of the amp itself. An amp should amplify the signal with an iron fisted grip and not add much of anything of color or flavor to the music. It did exactly that.
In the end the WOO and Audeze amps made the cut and stayed. That’s only because I like a more romantic and sweeter presentation if not exactly accurate like the professional grade SPL presented the music with.
The Bryston was slightly leaner and more forward sounding compared to both SPL and Violectric (another German professional grade headphone amp).