To be honest, having 2/3 "real" speakers in each earpiece doesn't make them a true "surround sound" solution. Surround sound isn't meant to be experienced with the noise coming from an inch around your ear, they are meant to have distance between you and each source.
5.1 Headsets are a bit gimicky in my mind, they do a poor job of giving you spacial-awareness, sacrificing audio fidelity and stereo-listening (ie. music) in the process.
Stereo headset are a much better choice, simply because you lose all the downsides of 5.1s and also can give good spacial awareness. Simply put, you have two ears. You don't have 5.1 of an ear, that means that you can discern directional sound in the real world by listening to subtle pitch shifts, loudness levels, etc. not direction per-se.
Take a listen to this:
(Make sure you are only wearing STEREO headphones... Then close you're eyes.)
This is an example of what *could* be possible in the future, using software surround sound emulation (such as Dolby Headphone or CMSS-3D) with a set of stereo headphones. Dolby Headphone and CMSS-3D already do a half-decent job, and they are getting better all the time!