Planning to buy the fiio x1 gen 2 and AT m40x as my portable setup. Is it a good combination?

When I use them with the dragonfly on my mac everything works great! Also with my ipad and iphone. I assume the problem is Hd 598 are easy driven 50 ohms headphones and not really made to be connected to desktop headphone amps, desktop headphone amps are simply made for more hard driven...

I own the Sennheiser 598 and are very happy with them, they work perfect with mac mini and dragonfly!   Now to the problem: when I want to connect them to my main stereo ( naim nait 5i + cd5i) I getting  volume unbalance in left and right channel on normal listening levels when using headphone...