You most likely got a new DX90. It takes at least 150 hours to burn in and sound better. Using the inclosed resistor plug in, that they include for this reason, would be what I would use to keep it running all the time on repeat.
You bet! I have enjoyed them for years, in fact I have 3 pair. 1 rewired with very expensive stuff, that improves other phones but for the PPs, I like them with the stock cable. I just use the foams that have about the size of a quarter taken out of the middle. The mids improve some and the bass is even cleaner. The pads cost about 5 dollars or so. Inexpensive fun and a true bargain.