Correct. That's very roughtly the scalability margin that a system based on the Bartok leaves on the table vs. top echelon systems in my own opinion and experience, especially when dealing with complex acoustic music and when you have a TOTL headphone like the Valkyria, the AB-1266, Susvara, SR1a, etc. Note that to improve over the Bartok you don't necessarily need to spend multiples of its price. With the Bartok, dCS makes us pay (and rightly so) for the convenience of a superb sounding, nicely packaged AIO system. By investing a significant effort, time, trial-and-error based on your own taste, you will be able to put together a separates system with a markedly better sonics vs. price ratio.
Yes, if you are fully committed to acoustic music. The transducer is still what counts more in a hifi system, and I haven't found another headphone (yet) that provides a more lifelike reproduction of classical ensembles of any size, with and without vocals, piano (especially), small jazz groups. So if this musical content is your thing, the Valkyria is - again, to my ears - the best option even if you don't max out the rest of the chain with silly-money gear.
Valkyria + Lotoo Paw Gold Touch Ti has been a hugely satisfying listening, for example, easily beating most desktop setups I have experienced - with the best suited music for the Valkyria.
There are much cheaper headphones that can surpass the Valkyria regardless of the amp, depending on your tastes and your preferred music genres. For example if you are into modern pop, electronica, hip-hop, metal there are plenty of better options at a fraction of the V. cost.
That is mostly related to how power hungry the headphone is and what genre you prioritise.
If you avoid excessively power-hungry headphones like Susvara or HE6, and focus on synthetic music only (where the entertainment factor overcomes the reality check), the % of sound quality you leave unexploited from a Bartok used as an AIO will be much less than 25%, and most likely it would become more a matter of flavor than an objective better / worse. I am aware that this sounds like the usual snob-like dismissive attitude towards popular music from a middle aged classical / jazz loving audiophile (that's what I am after all
), but it is my honest opinion. Of course, YMMV.