I have a monoprice 8323 as well. It's a great sounding set of cans. I have a JVC HANC250 that this replaces which I paid about $100 for years ago. The 8323 is amazing and destroys the sound quality of the HANC250. Its also excellent at isolating noise.
For now, I use my 8323 through a Creative Labs 70SB072000000 Xmod USB Sound Card. It sounds great, I love the 3d effects- it sounds like surround sound- even though it's likely possible to get similar sound through a software program or plugin. Anyway, the xmod sounds good although it's not a true amp/dac.
Anyone use one of these Xmods? Is it worth an upgrade say to an Fiio E07K? What will be the difference in sound be? Does it have to be a flac file to hear any difference? How much difference will a desktop vs. portable amp/dac sound? Looking for audiofrog quality, naturally.