After a long time of researching for monitor headphones, I ended up with the DT-880 Pro, having previously heard the regular version from a friend. It's the first day I'm using them and I admit that the headphones are something else!

Having also listened to the AKG K-712 and worked with the DT-770 (at a radio station), I found a solution for writing/mixing music during late night hours. Insane detail in the lows (I heard things that I hadn't heard on my Yamaha HS-8). I'm inputting them from a Motu MK3 Ultralite without any issues with volume. Just enough to not damage your hearing (the phones on the card are set at -1db).

The build quality is unmatched. Lightweight yet solid enough. The cable is amazing, a light spiral that doesn't bother you to move it around (until yesterday I was using the Sennheiser HD 25C II which had a huge and heavy cable).

If you're into music production or even just music listening, the DT-880 won't disappoint you.

Having lived with them for almost a year, they managed to put much more expensive headphones in the drawer.
For their sound quality, they are the ultimate value for money.
Regarding driving, they require an amplifier since they are 250 ohms, and they are driven wonderfully by both FETs, transistors, and tubes.
Among the amplifiers I use, one is a DIY clone of the Beyerdynamic A1 (from the kit that is circulating with some modifications that I consider necessary) which I drive with a tube preamplifier using a pair of 6AK5, and another DIY tube amplifier with 6L6 in a triode configuration and output from the cathode.
With both, I have incredibly good results without distortion or clipping at high volumes.
The biggest confusion for anyone deciding to buy them is the choice between the 770, 880, and 990, and after listening to all three in the store where I bought them, I can say that choosing the 880 was a bit like "oh, whatever" since each model has its own unique characteristics.
The 770 is for isolation and bass, the 990 has poor bass but perfect stereo image and crystal-clear highs, while the 880 is in the middle. (We're not talking about huge differences, they have the same drivers and the difference lies in the enclosure tuning, where the 770 is completely closed, the 990 is open, and the 880 is semi-open with restrictions).
Both the 880 and the 990 can be easily modified if someone has knowledge of the 770, while the opposite requires drilling.
The earpads are made of velvet, which may require regular washing during the summer months due to sweat, but if you see how velvet is washed, it's not something that causes difficulty.

edit> Exclusively for DIY tube enthusiasts, I made a low-mu stage (6SL7+6L6) purely as an experiment. Anyone who searches for a related schematic will find it with EL34, but no matter which tube you use, it's exactly the same) and I have to say just one thing: try it! (ideally as a pro, not with amplification) and simply listen to a mediocre recording or an old bootleg (okay, not completely terrible, let's say 128 kbps).