Rather, it's more precise with VR sound (kinda like binaurial, but dynamic, allowing you to move about in 3D space and for the sound to be effected dynamically, as opposed to prerecorded binaurial audio which stays statically locked to your head). Speakers offer more discrete channels of audio, but that doesn't necessarily translate to a more accurate sound field.
e.g. 21 channels assumes that there are 7 channels each arrayed top, middle and bottom. It won't be able to accurately replicate sounds coming directly above or below you as you move around.
Also, it'll be difficult to achieve the real advantage of VR audio - which is been able to move around a sound source. In the Technolust startup screen, there's a sound source placed in the middle of the room (just behind your starting point). You can move around this source and pin point exactly where it's coming from, even if you can't actually see it. No amount of surround speakers would allow for that sort of functionality.
Any headphone will be adequate. But for the best experience, integrated audio (such as found with the Rift) should be used, as it provides you with a mirror of the sound engineer's intent, without variation.
Different headphones might effect subtleties in the sound that effect how we determine the location of audio, making something appear closer or further then it was intended to. In this sense, it's not dissimilar to using different pairs of lens with a HMD. It'll still function, but distortions will be present.