We all seem to respond a little differently to the different implementations. Some people seem to get good positional cues from the microsoft headphone implementation in DirectX but I don't find it to work at all beyond anything but stereo for me. I did get some positional cues from Dolby Headphone but I found it wasn't very accurate and front to rear was a real problem, I couldn't tell them apart. CMSS and SBX Pro both gave me reasonable positional awareness and I can tell front from rear but the sound was hollow. The GSX 1000 is as better for positional cues and it doesn't sound hollow but its also not like real life yet either.