I have really tried to read all posts on forum, and got confused, probably because I read posts related to older version of vMix. Hope that someone have time to help me.
My main goal is to make 24/7 stable configuration to put into rack and forget about it. Load on system should not be more than 30-40% of CPU and GPU, so that I can add more features later on. My main concern is not to make mistake and buy something incompatible. And recorded files should be in best quality that we can get for 4Mbs.

System will have 4 SDI 1080p 25fps inputs. All inputs will be recorded via MultiCorder in mp4 (4Mbs) as well as Program output. I will probably use Replay option. Same PC will be used for streaming inputs over http in low resolution (around 430x240px).

1. What motherboards are proven to work with Megawell XI400DE-SDI or Pro Capture Quad SDI cards. Megawell is preferable card due to hardware processing ( vertical flip, color processing )?
DDR3 is preferable memory, due to latency. I was thinking to have 4x8GB. Or should I go with 64GB DDR3?
2. Processor. Should I go with some that have integrated graphic card and QuickSync ( i7-4790k ) or with more cores ( i7-4930k or E5-2680 v2 )?
3. Graphic card. What does Hardware Encoder needs? I read in many places that GTX 750ti is enough for vMix systems. But since new Vmix supports NVENC, is it better to have GeForce 9XX card ( encoding up to 2 channels ) or Quadro ( encoding up to 6 channels ).

Thanks