If I were looking for comfort of Sennheiser HD 558 or Philips SHP9500 (this one is open-back) but more compact so that they could be used on the go, what would be my options for under $300? Could on-ear cans be comfortable? If over-ear is the only way to go, are there compact models that provide...

What are the best full size headphones (closed or open back) under $100 that don't require a dedicated amp or DAC? Listening material is very diverse so closer to neutral is probably better. Must be very comfortable (pads, clamping force etc) for long listening sessions so that ears don't hurt...