In my point of view and as others say, x6 has a sound character on the bright/transparent side. This can irritate some ears. But combined with a tube buffer it can reveal musicality in a very "hi fidelity" warm way. There are also options of tube emulation, through VST fx plugins in foobar.
It could fit then on systems with already deep bass capabilities very efficiently with good control.
So, I like the sound of this device (as a DAC), it is a good source for further improvements. For me it could be useful to have a close to "natural" source and then try to "warm" it.
It also works very efficiently with ASIO drivers I have posted previously, never dropped a sound, very good cpu management, tested for days.