Going from an SR-225i will make you a bit sad..at first. They just sound so different to me and I have both. I love both of them.
It's best to just not compare them and learn to enjoy them for what they are. Comparing the HD-598 to the SR-225 to much would make me hate the HD-598!
The HD-598 will be much warmer, a lot smoother sounding with less treble, sound clarity and detail. The HD-598 does have some engaging mids, but not as engaging as the SR-225, but that's a good thing sometimes.
The HD-598 is not even remotely fatiguing to me, but not as boring as the HD-600.
HD-598 definitely has a much larger soundstage. I think it's same to say the HD-598 will be better for more genres. SR-225 definitely seems like it has less bass than the HD-598, but more treble and more forward mids.
Since the E7+E9 is a fairly bright setup to my ears, it'd be a very nice match for the HD-598 I think. If the HD-598 is fatiguing (it should NEVER EVER be for most), try removing the E7. Should be perfect though.