One version of HDVD800. HDVA600 is same amp without the DAC.
As far as I know, only one color, silver.
The DAC in the 800 is only OK. You might want the 600 with some better DAC, The DAC chip I believe is a Burr Brown 179_something. They don't say in the manual. I had a Denon DVD3930 player with a 1796 chip which was awesome but the player became problematical so I switched to Marantz SA8005 with a Cirrus Logic chip which is equal to the Denon and more reliable. My Oppo 95 with a Sabre 32 DAC chip is excellent too, even more detailed than the Burr Brown or Cirrus Logic but a bit bass shy at times it seems.
Used is fine. I bought mine used for $1400 on eBay from some high end dealer in Boulder who took it in trade for some Macintosh gear. No problem with this guy. But with eBay there always is some possibility. Just watch who you're buying from___buyer feedback.
Or you might want the Sennheiser Orpheus. It comes with both the cans and the special amp for it. Only $55,000. That's right, and the right number of zeros too. You can google it and drool.
The HD800 and HDVD pairing are excellent. I tried a Benchmark DAC2 HGC $2000 which did not improve upon the DAC in my CD player, a Cirrus Logic something or other. In addition to the chip used, the output quality of a DAC may have something to do with other electronics in the output stage too. I am happy, you will be too with the rig your are contemplating.
The only thing I would recommend to save bucks with an amp is Creek OBH-11 $225 which can be had used for about $100. It has good synergy with the HD Sennheisers, both 600 and 800. I tried a $1300 Burson headphone amp which didn't work out too well. The only way to approach this stuff is to listen to it. The proof is in your ears. It might be a good amp with good synergy with some cans but not mesh well with yours.
Buy the HDVD 800, or 600. You won't be sorry you did and finally settle the matter instead of driving yourself crazy wondering what to buy forever and ever. I did it and am finished. If I wanted something better I would have to be thinking of LCD4 or Abyss with Cavalli Liquid Gold amp or Pass Labs new thing;..............$7500 to $11 or $12,000 total, somewhere up in those brackets. And I am not taking this hobby that far.
Now if I can just figure out how JRiver works and how I can integrate with this spiffy new Onkyo DP-X1 portable player I bought. Hmmmmm, I'm getting there. Do you know anything about JRiver and how it works? Do I load the playlist onto the SDXC cards from JRiver or put the card in the player and find it from there through the USB connection?
Good luck to both of us.
Bill