Thanks KG Jag.~
Is your music source a Windows PC? Mac? mp3 player? etc.
The Senn HD558 with the black rubber tape removed from inside the cups, has some decent bass.
And it's only 50-Ohm, so does not need much of an amplifier, which leaves more cash for the DAC.
The Beyerdynamic DT990 Pro 250-Ohm is good for the concert hall feel. but need more of an amplifier then the HD558.
My source will be a Windows PC > Foobar > Fiio E17 (currently.) Also, $300 isn't my complete budget. That's a slice of a larger budget that I've set aside for headphones. Total budget is gonna be around a grand.
I'm a bit worried about the DT990's as I've read they have recessed mids, which is what killed the M50 for me. I recall really enjoying the 598. So, I'll consider the 558 with tape mod, for sure. I'll probably re-listen to the 598 when I get the chance to make sure.
I'll definitely consider those for options before I foot the bill for the HD650, Schiit Asgard, and Schiit Bifrost.