tbh i'm not sure there's a big enough difference between the hd598 i had and the k712 i have. at least not enough difference for the extra cost of the headphones and needing an amp on top. Maybe hold off as the hd598 might come up for £75 in the boxing day sales again. It was the all black se version too (god knows who put the cream and brown pair together in a brainstorm and thought they look good)
Just my opinion
Just my opinion