I've read, that Dolby home theater v4 has no real virtual surround effect - it has just a stereo widening effect.
Seems like a lot of people who get used to dolby headphone on previous Xonar card questioning this. I`ve done some researched on the internet and also with my personal experience after using the phoebus for a month. Apparently, they replaced the dolby headphone features in phoebus with Xear Surround Headphone. Both has almost similar feature which is taking 7.1 signal from windows audio (it can be games, movies, etc) and virtualized it through stereo headphones so you`ll get directional surround sound from your stereo headphone.
Unlike Xear Surround Headphone and Dolby Headphone, The Dolby HT4 will only takes 2 channels from windows audio (It also can be games, movies,etc) and if u activate the surround virtualizer on the HT4`s control panel, it will only gives you virtualized surround sound from 2 channels audio. so that means, HT4`s surround is just pretty much like stereo widening effect and not directional surround sound featured on Dolby Headphone or Xear Surround Headphone.
You can check it by yourself, try to thick the Xear Surround Headphone option on Phoebus control panel and check the right click on volume icon on taskbar -> click playback devices -> right click on asus xonar phoebus (headphones) -> properties -> click advanced tab
you`ll see Xear surround 7.1 in default format drop down box, that means windows will gives information to the games or media which you play that you are using 7.1 audio setup, therefore the games will send up to 7.1 audio channels (depending on the game, most games used 5.1 channels) to phoebus and xear surround headphone will gives you "dolby headphone like" directional surround sound over stereo headphones.
Hope this will help most peoples who got confused about it.