If you want to plug both the headphone and mic into something external then your options are limited.
If budget isn't a problem then the Creative Sound Blaster X7 is certainly worth a look. It has a powerful and versatile headphone amp, excellent DAC, high quality ADC (for the mic) and can even drive passive as well as active speakers. The downside is cost, as it weighs in at a hefty £289
The Creative Sound Blaster G5 boasts some excellent specs and is a much more reasonable £120. However, some people have complained that Creative have "messed up" the surround sound for gaming compared with sound cards such as the Sound Blaster Z and ZxR.
The Asus Xonar U7 is another well specced box of goodies that uses Dolby for it's virtual surround features rather than the SBX of the Creatives. Coming in at £80 it is something of a bargain and as long as the headphones don't provide a difficult load (the Beyers don't) then it is good to go.
Lastly, there's the new kid on the block, the Sennheiser GSX 1000, which boasts an in house, top of the line DSP for their surround features, which they claim are the best available. Superb build quality, highly respected brand name and user friendly interface plus it looks a LOT better than the competition. All this does come at a price though, it's currently on the rain forest for £200 but if you want the best, then this is probably it.
OcUK Sennheiser GSX 1000 discussion
If you don't need virtual surround and are happy with stereo, plus you don't mind plugging the mic into the motherboard, then the recommended "cheap Topping" would likely do the trick although there are many, many external DACs and headphone amps out there that would do that trick better, as long as you don't mind paying for them.