jocar37,
I too am a newbie, and I will be of no use with the computer audio....because I'm learning there as well. I was in a very similar situation as you are. I decided on purchasing an Onkyo C-7030 over the Oppo BDP-103 and the Marantz CD-5004, mostly due to value for price and the fact that I wasn't going to use the on board DAC. Instead I purchased a Maverick Audio TubeMagic D2 DAC w/ OPA627 OpAmp & NOS GE5670W tube upgrades, after trying and/or considering some fine units from Fii0, Schiit, Emotiva, and Topping. Headphones are Sennheiser HD558 and Grado SR80i.
In addition to terrific reviews and very reasonable price, I liked that the Maverick has a full variety of inputs (USB, BNC coax, coax digital, and optical digital), and it also has a vacuum tube pre-amp output stage in addition to the normal solid-state audio output. With the Maverick I use the analog normal to drive the output to a Bob Latino VTA ST-120 tube amp for my Thiel speakers, and I use the the tube pre-out to drive a Schiit Magni headphone amp. I particularly like that the tube pre-out softens digital tendencies, and of course I never have to change cables!
I have just gotten through the equipment break in stage (critical with this many tubes), but I will admit that in 30 years of very high end audio I have gotten more involved with the music that is provided to my ears. Headphone use is relatively new to me, but I am captivated by the way the Maverick/Schiit combination can deliver open, detailed, wide, quick paced, music over a wide range of media. Mids and trebles are detailed in every way, and the lows are punchy and more than adequate....but bass freaks and techno fans may need to look elsewhere. I was confused how sound stage could be present from a pair of headphones, yet there it is. My only difficulty is that on very rare occasions, and I cannot put my finger on it or describe it well, a small void or opening appears in the stage. A minor annoyance, and I'm sure it will be resolved with some cable swap or tube roll or such.
Prior to changing out my equipment, I really did not enjoy the Grado headphones for much more than short periods of listening, all of the cliché's.....fun, bright, uncomfortable, fatiguing were true for me. I found myself reaching for the HD558s for all but a quickie with the Grados. Now all that has changed, I find myself enjoying both headphones much more; I now find them "different" from each other, not one better than the other.
Not sure if my experience is helpful for you, and sorry I'm not very good at the "audiophile" verbiage.