here is something which throws a wrench into the gearbox per se..
perhaps partly my fault for not listing these with "external dacs" above but my mind was thinking along the lines of hifi-audio solutions (which are stereo sound only without virtual surround capability). technically the below are external dacs as well but are marketed towards gamers so it slipped my mind for a few.
bear with me here as this will take a little explaining...
okay so i DID find some products which might work with the ps3 and maybe the ps4 and give it virtual surround capabilities similar to the pc soundcard. many of them are also compatible with pc as well and you've probably heard of them before. the best way of thinking of the products is that they are like external soundcards (so like the dx) but cross platform compatible between consoles and pc.
earforce dss
http/www.turtlebeach.com/product-detail/accessories-legacy/ear-force-dss/239
recon3d
http/www.ebay.com/itm/Sound-Blaster-Recon3D-3D-THX-USB-External-Audio-Enhancer-SB1300-PC-PS3-XBOX-Mac-/251724393186?pt=LH_DefaultDomain_0&hash=item3a9bf16ae2
mixamp
http/www.amazon.com/ASTRO-Gaming-MixAmp-Pro-playstation-2/dp/B00NY5ZNZA/ref=sr_1_1?s=videogames&ie=UTF8&qid=1432475813&sr=1-1&keywords=astro+mixamp
i'd ignore the recon3d due to it being completely overpriced.
i believe the astro mixamp is compatible with all of your devices (please check for yourself though) and will offer you the virtual surround you want. generally something similar to this
http/cdn.head-fi.org/4/42/500x1000px-LL-4212849e_750524.jpeg when hooked up to devices.
the dss listed compatibility for all systems right on its page however turtlebeach really isnt known for super high end audio (its famous for generic sounding gaming headsets). it says its compatible with any analog headset.
now the kicker....
if you used such a product it would be a waste to have a xonar dx as your soundcard as the external device would be doing the processing instead of your soundcard (when youre using it with the pc that is). now i mean you could use the device with your consoles only but its quite a bit of cash to invest for just a console specific device and use the dx for pc. possible, but that would be $200 spent on dacs alone.
such a device would take the place of any sort of usb adapter you'd need for consoles with a 3.5mm headset so it does have merit in that regard as well.
the mixamp is rather popular though i'm want to say the dx is a much better card. its known that the stx blows the mixamp out of the water and the dx uses the same dac as the stx (Just doesnt have the amp). so i think for a pc solution the dx is better. however the dx is pc only while the mixamp is a cross platform solution.
the three options:
-use one of the above (say the mixamp) with all devices. no soundcard on pc. (virtual on all devices, cross platform)
-use one of the above with consoles only, use soundcard on pc. (best audio quality on pc, all devices have virtual support)
-use just a soundcard on pc, just an adapter for consoles for the headset. (limits you to stereo sound on consoles)
honestly is virtual needed? its a personal thing. i've had many people here i've set up with a soundcard which gave virtual as an option and bought wide soundstage headphones come around and say they dont use virtual since the soundstage is wide enough on its own. then i have some say they love virtual. its not a clear cut decision and you need to listen for yourself. generally i'd say its not absolutely required though.
since you will be getting an amp, you dont need the stx over the dx. they use the same dac and the stx just includes a better amp which you dont need.
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with all the above i'm thinking you'd likely need a post back for clarification since i gave you a few more options to think about.