Reply to My track sounds less punchy when I export it as a wav than when I play it in Reason

Hey all, I've noticed that with this dubstep track I'm working on, when I export it as an audio file to WAV it sounds far less punchy than when I just play it inside Reason. It also seems compressed, i.e. it loses much of its dynamic range, but not in a good way! I haven't noticed this happening before, but this is only my second full track.

One thing that occurs to me is that when I listen to it in Reason, I have the master volume down so it's not too loud on my monitors (I plug my monitors straight into my sound card; there is no mixer in between), but in order to get the level loud enough I put the master fader all the way up, so maybe that is compressing the sound (because the levels on the mixer go all the way to the max)?

Any ideas what is going on? Help would be greatly appreciated!