well i dont know, as i've only got sennheiser pc-350.
as a first impression for asus xonar essence - no big deal, really. i mean, not one worthing double the price of creative x-fi titanium.
dolby headphone? a disappointment, very little effect added. no, it does not fill your head as i would expected.
as for the amp, yeah, you do get louder signal (my senn pc-350 is 150 ohms impedance, so it needed that) but thats about it. i didnt necessarily perceive a rise in sound quality.
ok, i've only listened on asus on 2 games so far: dirt 2 (sound ok, apparently a bit more sounds audible than with x-fi titanium) and gta4 (disappointment, sounds appear like from inside a barrel). also, some music but of low quality signal.
i'll try some further testing today and if i dont like it, ill just send asus back and keep the x-fi titanium. OR, send it back and ask them to send me instead x-fi titanium fatality pro (unfortunately though, i will think twice about that, as ive heard there are still no drivers for windows 7 for fatality card)
so in the end, i may be glad i didnt get to sell my x-fi titanium as yet.
Aynjell: i didnt order the furbar 4 amp anymore.