They are a good headphone, especially if you're a mild to heavy basshead. It's a very fun sound, with a very good soundstage (the biggest I have heard in a closed headphone, surpassing some pretty good open headphones). They are incredibly comfortable as well. It's a great starter headphone for those that go directly to mid fi price range.
They won't need MUCH amping to sound good, but they do need an amp. The bass is very prominent, and can be very slow and uncontrolled. The highs are great (enough to satisfy trebleheads like me). I don't put a LOT of stock in the mids like a lot of people do, but I do prefer a brighter sound than the Pro 80s. In any case, they were fantastic back when I owned them, I just grew out of them, that's all. If you buy them and build your equipment, I have no doubt they'll make a lot of non neutral heads very happy.
Since I found it a bit warm, I honestly wouldn't recommend tube amps as it'd just make them too warm for my taste. A good transparent solid state amp would fit me best if I still owned the DT770 Pro 80s. I think they would be a perfect match with the Fiio E9 (with the E7 as DA or some other DAC of your choice). They aren't very hard to drive, so even a lowly Fiio E5 made them sound great (which is what I used back then). They could only get better with more power to juice them.
