My current setup is as follows: Windows 10 PC running iTunes 256k AAC or streaming service of my choice to a Fostex HP-A4BL DAC/amp via USB. My headphone of choice at the moment is a Fostex TH-X00. I am enjoying the sound quality I am getting out of this setup but I am fairly new to personal audio and I want to diversify and improve my gear selection as I move forward. For reference I mainly listen to EDM and electronica but do also enjoy some modern pop (Adele) as well as Classic Rock, Opera and Jazz. As for my goals, I would like increased resolution, detail and soundstage (on music that could take advantage of it - EDM obviously won't) while not loosing the smoothness or strong bass inherent in the TH-X00. I have considered first upgrading my headphone to a more ToTL offering and was looking and researching in that direction but am now wondering if maybe a good DAC might not be a better initial purchase? Would the rather inexpensive DAC chip in the Fostex be able to do a ToTL headphone justice and therefore make a good R2R DAC a better buy? Basically, I have read the advice threads we have at the top of this forum but I am still a little unclear as to what might be the best option from where I am now and for where I want to go next. I should also note here that I do own a Schiit Lyr 2 with stock tubes so I do have an option for a stand alone amp if the DAC is the better choice. I would like to keep the next upgrade under $1500 and I do appreciate any and all words of wisdom.