Thanks for liking my setup dude ^^
The component names for my setup are named in my original post.
However, my project was extremely expensive, and I would not expect others to go as far as I have done. Plus, this is Plan A Setup; Plan B is my true final setup which I am working on next year (swap Onkyo DP-X1 to Oppo Sonica DAC for source, and get two DHC Prion4 3-Pin XLR cables).
For your HD650, a decent DAC/source and cables are needed.
First, are you using a single NuForce HA-200, or two?
Starting with source, make sure you use something with high VRMS output. This means high voltage output from the source.
For a balanced setup (2x HA-200's amps), between 4VRMS - 8VRMS or higher will do the job and let the monoblock amps sing. 2VRMS will suffice but will not be truly adequate, but it is doable.
If you are only using a single HA-200 amp, 2VRMS - 4VRMS is good, anymore is ok but I think overkill.
Your source can be a digital audio player, or desktop based. Good examples include Astell&Kern KANN, Oppo Sonica DAC, iFi Audio Black Label, Chord Hugo 2, and more.
Next, cables. This is a wild area and I cannot tell you what to buy or get, but here are some suggestions:
If you live in a country that does not use US mains power plugs, you will need to purchase appropriate mains power cables. A single HA-200 requires one power cable, so two amps will need two mains cables each.
A single HA-200 takes in a standard audio RCA cable (stereo Red and White) for single-ended playback. The output is 6.3mm headphone jack, so a cable or adaptor is required for your single-ended headphones.
However, if you have two HA-200's, you will need balanced 2x 3-Pin male XLR cables (or a single balanced cable, such as 2.5mm male TRRS, or 4-Pin male XLR, that ends in 2x 3-Pin male XLR jacks for each amp) from source to each amp.
Then you will need a headphone balanced cable; here it can be a cable that is terminated in either 2x 3-Pin male XLR jacks for the front of each HA-200, or 4-Pin male XLR and then use an adapter (4-Pin female XLR to 2x 3-Pin male XLR). Your headphone (earcup) jacks will be ones for your HD650.
As for what are good cables, this is very complicated.
In summary, I prefer high gauge pure silver, but good gauge pure copper, or good gauge copper/silver, are excellent.
I recommend Moon Audio, and Double Helix Cables, but this depends on your budget and time.
There is a lot to consider, but, hopefully the above helps you on your own setup plans.