So I picked up a cheap Turtle beach DSS2 sound processor on Ebay for 30GBP. It takes the Dobly digital output from the optical out, and does some sound field processing to output to your stereo headphones, using the Dolby Headphone technology.
I set it all up and tried it out, and at first I thought - well it’s clearer but the sound placemtn is not that much different.
Then I flicked over to stereo mode and wow! You would not believe how good the surround effect is from a standard pair of headphones. You can here the camera chopper fly over you front to back, and the sound of a 787B on your tail dodging to your left and right to try and get past you is really cool.
All in all I’m very pleased with the upgrade.