Yes, every part of the chain can have an effect on the output. However, with the same amp, these two cans have their similarities and their differences.
Let's forget for a second that one is mostly closed and the other very open, they both produce a very appealing rich tonality. The D7000 seem to dig a bit deeper because of a bump in the upper bass. This causes them to have a bit more 'slam'. The roll-off of the highs on the 650 give them a very laid-back characteristic, and make them, yes... more 'forgiving'. Even with a lot of power I still found the 650 a bit to 'dark' or veiled (yes, I know that word causes 650 lovers to have fits, but it's my opinion, and how I heard it).
The D7000 has very clear and clean highs that are too diminished in the 650 for my taste. I tend to like things fairly detailed and bright. The 650 did not have the crispness of a live performance, and did not produce the 'air' necessary for instrument placement.
Some talk of recessed mids in the D7k. I've never found them recessed. Vocals and strings are very forward and present.
'Soundstage' is a word used too often in reviews and opinions are all over the place, but I'll say that the effect of the closed D7k is a bit more intimate than the 650.
Both very good, and it comes down to taste as they produce a very different take on the music. Yes, your amp will probably make the 650 sound even warmer than how I experienced them (but they ARE 'warmer' to begin with. Also, much depends on your source. What are you listening to... type of music, type of files, etc.
All these things are factors. The 650 will be more kind to heavily compressed mp3's. The D7k will be more truthful to the harshness of some mixes or compression artifacts.
Good luck.