Some more impressions..
Turns out I've been listening to mostly normalized music since my main playlist I use contains many different songs.
Anyway I'm using foobar2000 now with standard FLACs (not normalized) and soundstage difference is huge. I'm really impressed.
I just found an album in my collection I bought on HDtracks half a year ago that is great for testing headphone performance (although this is mainly for headphones but still):
HeadFi and HDtracks - Open Your Ears
Let me just say that RE-400 passes the test with a good grade