Bought an EF2A amp and I'm loving it so far. I'm using it with my Denon D2000 headphones and it really makes a huge difference.
Now I'm looking for a good pair of open headphones to pair it with. I don't really want to spend more than $300, but I could go up to $400 if there really is a big performance gap. Also, I'd like something that'll be a true upgrade from the Denon's. I want them to be well balanced and have a very good soundstage (important for me), and I don't need something super bass heavy; I prefer a tight, punchy bass that stays in it's place. I want it to be there, but not overwhelming. I really like to be able to pick out and focus on the details in music. I mostly listen to folk and indie pop music, also a wide variety of punk rock and metal. And I'll be using them for games and movies.
Beyer dt990s, which are $145 on Amazon for the 240ohm model (seems like a great deal)
Hifi-man HE-400: on sale for $300 right now
Grado sr325is- $298 on Amazon
I'm open to other suggestions though. Also, there is a decent audio store near me that has a lot I can try out. They also have the EF2A, so I can try headphones with them, which is nice. Will probably go tomorrow to test a few out. This is what they have in stock.