For me personally not much. (384 btw. would be DSD territory, 192 being the highest "regular" PCM type encoding)
For the longest time I have used the optical out on my Macs (since USB has been a mixed bag, even though nowadays it's becoming more and more widespread). Since that one too is limited to 24/96, it has never been an issue. (192 over optical is not really standard anyway) The various iPods (and their digital docks) are even lower, so not the least limitation on the M-DAC end.
I have had some 192 tracks for a while, for comparison (from various sources like HD Tracks etc.), using my AK100 which fully supports them, in straight playback, but also fed to the D18 via optical (after I got a cable capable of handling that frequency), then to my Woo amps. I have never for the life of me, in any combination of equipment been able to hear a difference between the 192 & the 96 version of the same tracks, and long ago decided the 192 just isn't worth the extra cost & storage space. For that matter, I mostly buy HD to get a good master more than the higher resolution. The vast bulk of my music is ripped CDs, quite a few from before the mid 90's, when the whole loudness war really got out of hand. I value the quality of the recording far more than the resolution. If all things are equal, lossless is important, any HD (over 16/44.1) just the icing on the cake.
And most recently I got a DSD sampler that included equivalent PCM formats (192/96) Once again, I could not hear a difference, no matter how much I paid attention. It does nothing for me, and I'm certainly not going to re-buy music I already own, at least in standard lossless. And that leaves very few records in DSD I would interested in. Maybe things will be a little different in a few years... (in terms of offerings, not in terms of audible improvements, and for that matter I don't think my ears will get better with the years : p )
So you have to ask yourself: How much of that stuff do you already have in 192-and-up formats? How much (money) do you plan on spending on acquiring it? Are your favourite albums & tracks even available in those formats? Because it should ultimately be about the music...!