Is there any reason you didn't consider the HiFiMan HE-400?
It's surprisingly forgiving of underpowered sources, and has bass done right: that is, punchy, cinematic bass whenever the source calls for it, but only when the source calls for it, thus not exaggerating the bass when it shouldn't be.
Also, it's surprisingly comfortable, even over the long term.
I did look at those. Wayyy out of my price range. I would if I had the money :(
I'm going to go with the DT 990!! The 250 Ohm Pro is the cheapest ($175 on eBay), so what would I need to bring out it's full potential? I doubt just a sound card in the $50-$75 range will do it(correct me if I'm wrong), I'll have to get an external amp right?