I don't understand how price is not a factor...
Both the Mjolnir and the GS-X have preamps + headphone amps, except GS-x is $1,750 more.
I think you should pick the Mjolnir, because the differences between these amps will be subtle and too hard to determine which your prefer w/o actually auditioning. Your risk of buyer's remorse is the same, but your sunk costs w/ the Mjolnir will be less incase you wanted to resell it/keep it.
2nd I'd only consider the GSX if I had multiple other headphones that I wanted to use it with, as this amp is more versatile.
3rd I'd still be hesitant to buy the GS-X because I think the Bryston BHA is equally as versatile, has just as strong reviews, and is over a grand cheaper. Also I could buy a used WA22 and a Mjolnir for the price of that used GS-X, which would also be much more versatile.
Edited by rrahman - 2/14/13 at 10:36pm