I don't have a STX on hand to do a direct comparison to my NFB 15.32 with my DT880 premium 600 while building up the collection of op-amps again, I was going on based on memory, Other wise I would use it again to comment better. I do know I didn't like it sound signature of the JRC's in the i/V's When I had a AKG 702 which I always changed to LT1364 or the DT880 pro-250 which I changed to OPA2111AM. The thing which he does not mention is if he changed the op-amp from the JRC's to a different op-amp. That info is very important. If he still around might wanna ask him if he changed the op-amps,so you have all of the info. But then people ears are different, it might sound like that to him if hes using the stock op-amps, but to some one else it might sound totally different, including with different pair of headphones because of their sound signature as the results may varies based on the headphones that are used with the stock op-amps,If the stock op-amps was used. The thing you can send Dolby headphone thru out Optical/Coa into a external dac amp, so you can keep the features of the sound card, while getting the functions of the external dac amp.
Now I not good with explaining how every thing sounds my DT880 premiums 600 are not burned in yet since I got them 3 days ago, but the NFB 15.32 with my DT880 premium 600ohm's Sound clean you can hear every thing cleanly and hear alot of details, The mid sounds good to me and the bass is accurate and tight, there is no muddy or any thing. The highs does not hurt my ears I don't really know how to explain the highs that well or the mids. The sound stage is very nice and I glad my DT880 premium 600ohm is working very nicely with my NFB 15.32. I am using The Digital Filter settings Whch are Os 8 and Filter 2 which is 8x Oversampling,Minimum Phase Apodising filter, and I using High amp gain. When I had the A900X connected I used the Default filtering settings. THe only thing i remember about the A900x's with it is that the bass hit hard while being accurate and not boomy or muddy. it didn't bleed into the sound and it had a some what big sound stage for a closed back headphone, it did a good job for songs that had a lot of singing in it.
I can't realy explain how it sound while gaming to sum it up its very amazing, Totally different then how it was with the A900X's this was without any virtual headphone, I have use Razer surround software with my NFB15.32 and the software does a very good job, when the software is working correctly, I do have a sound card pluged into the Coaxial on my NFB15.32 but for recording reasons as in working ASIO. The Razer software works better then the Xear gear surround that comes with the sound card at-least. I do know how good Dolby headphone works, back with the STX and Dobly headphone, when I was using the AKG 702 with different op-amps, and DH does a great job when config correctly.