Coming to this thread extremely late.
Anyone else reading this should note that there are two completely different approaches to "5.1 headphones":
1) A special pair of headphones with multiple drivers built into each ear-piece.
2) A conventional pair of headphones with some fancy signal processing which simulates (at the ear) what you would hear if you were listening to a 5.1 track over speakers. (This is not as simple as it sounds, because you have to simulate the effect of wall-reflections in the virtual room as well as sound coming directly from the virtual speakers).
The Medusa 'phones which nico35 is suggesting fall into the first category. So do the Zalman 'phones (the ZM-RS6F) that tom-nieto is talking about.
The remainder are systems that go down the signal-processing route.
The best-known algorithm for this is called "Dolby Headphone", but there are others.
Devices that have dedicated headphones:
- The Pioneer device (the SE-DIR800C) uses Dolby Headphone, but (as far as I know) it is not available in the UK. It has fairly recently been announced in the US, though, so fingers crossed....
- Philips do two Dolby headphone devices, one with corded headphones (SBCHP1500), the other with cordless (SBCHD1500). Again, neither is available in the UK yet, to my knowledge. There are rumours that the cordless one may become available soon. I asked Philips customer support about the corded version the other day, and got several different answers - the most recent one reckoned it might be available here in September.
- The Sony MDR-DS5100 is a similar sort of product. It uses Sony's proprietary algorithm rather than Dolby Headphone - I don't know how the two compare.
All of these come with their own headphones that you cannot opt not to buy, which is a pain if you want to use better quality ones.
Expensive possibilities:
- The dual-SHARC verion of the Tag McLaren AV32R processor has a Dolby Headphone option, as does the AV192R.
- The Denon A1SR has Dolby Headphone output.
- As previously mentioned, there's also the Marantz PS-17, a rather elderly device which provides 5.1 channel processor/pre, but only two channels of power amplification.
Other possiblities:
- The Denon ADV-M71 has Dolby Headphone capability. This is a little all-in-one sytem, which includes a DVD player, decoder, and two channels of (rather weedy!) amplification. It has 5.1 pre-outs, though, and the specs mention digital inputs as well as outputs. I've seen this for only about £350 or so - don't know how good the audio DACs are, though.
- Finally there's the Lake Technology HSM6240 "TheaterPhone". Unlike the others, this is intended for audio engineers who are monitoring 5.1-channel mixes. It therefore doesn't take a digital input. Instead it has a 5.1-channel analogue input, and does its own A/D and D/A conversion. Not available in the UK. Cost was about £500+VAT and import duty to import one from Australia the last time I checked.