Just a note, i'm surprised you don't have more replies as these are popular units.
I can't give you much of a comparison as I have only listened the the Moon unit. However the advise i got was that the Oppo was not going to win over the Moon 230 HAD. Although I have to think that it will pair well with the Oppo headphones. My experience is that you need to match the amp and the phones, that will create the biggest synergy. Having said that I found the Moon worked amazing well with with my Beyerdynamics DT 990 250 ohm and DT 880 250 ohm. As well with a " working " pair of AKG 240 D which I use for voice editing. My top pair is HiFi man HE 560 and while it was really good with those it really excelled on the Beyer and AKG. So good news is that its versatile.
I didn't need all of the back panel of the Oppo and in fact you are paying for that use it or not.I thought about the Oppo because i have an Oppo BDP105 and really like it. But i usually go with the advice if my audio store guy which hasn't steered me wrong yet. I have a couple of DAC's and while I was told the Moon was not the best DAC , that it was a much better head phone amp, I didn't find that to be true. It bested my Resonessance Labs HD in the bottom end and soundstage by a full category, if i could use that classification. There is something about the "energetic sound" of Moon that makes me really like it. I'm not saying that sound is forward at all but it gets you into the music. When I listened to the demo model at home I thought i would play for say 30 minutes per headphone to try them all out and found my self on for hours re exploring some new download titles. Moon describes their sound a " visceral bass, transparent mirage and smooth highs" I concur that that signature is heard through the few products that i have heard so far. I would describe it a low lows and high highs with a great energy throughout.
I use mine in my home office set up, Audio engine A2 for speakers out of the back panel of the Moon 230, and the Moon for Dac / Amp playing headphones. In that purpose its an end game for me and portably gets an hour or two so use a day, when I'm working.
In my living room rig i have a Schiit set up and listen to Balanced so A you can't compare because its balanced and B the Schiit is a lot more money combined (USD 3250)
I previously had a Resonessance labs concerto HD feeding a Lake People ( Violectric) G109s. I really enjoyed that ( especially the portability) I was looking for something that had a proper back panel to run RCA out to powered monitor speakers. When i did an A B with the Moon it took less than 30 minutes to realize the huge sound stage alone was worth the change, I love tight bass and the moon gives that as well. the remote is a bonus that may or may not come in handy. Another thing on the moon is the lights that indicated the sampling rate of the music file, I'm always suspect of hi res downloads so somehow get a comfort factor here . For me anyways the way the DAc and Amp work together is well worth the 1500ish price. As i said in this particular set up it's my end game. If this was my only headphone set up I take a leap into another price category. Having said that I 'd do that with a separate DAC and Amp as the DAC world is a whirlwind of change and you need to make sure your going to keep your unit for a long while( in other words be really happy with it) or hedge you investment and keep it close to $1,000 . Another point, this is only me first Moon piece, but i did notice the used prices in their higher end gear seem to hold hight that average re sale for what ever thats worth. I thought that Oppo used to have a 30 trial but i don't see it anymore on their page,, I know Schiit does with a 5% restocking fee. there no remote for Schiit products but the do have some combos that would be in your price range. I personally would buy anything based on advertising, you need to hear it, we all hear and like stuff a little bit differently.
Hope that helps you
