ATH-A900s were my first decent headphones which I still use but they're old and I'm considering replacing them with something better (nothing crazy expensive though). What I'm looking at right now is the HE-400 which seems to be reasonably priced and is getting good reviews. Would you consider this to be a worthwile upgrade? I'm a bit worried of losing bass going from closed to open cans. I just don't want to be disappointed, I guess.