If you want punchier, more detailed bass you should check into the DT990. 250ohm should have more bass than the 600ohm I hear, but there's more detail on the 600ohm. The difference shouldn't be that big however, only that the latter model mightn't be ideal with Fiio since its output is max for 300ohm.
Edit: They're open, not sure how you would react to that. However, the soundstage is awesome.