Mac user needs a new windows rig for HDX

[recordingfun]

I have never bought a decent window cpu before and I will be on a budget here so Im thinking used.
What should I be looking for , I doubt I will ever upgrade past HD12
My last cpu was a MAC 5.1 8 core 2.7 mid 2011 20 gig .
Since it no longer works I need a rig to run HD12 but i need to do it on the cheap. What will work well, what I7 processor should I be looking at , how much ram , do I still need the second hard drive how much ram is effective (says 16g recommended ) am I better off using windows 7 or 8 than 10 , any particular makes I should look into, Also I were not doing this on the cheap used what should I really be drooling over. Im looking for no more than 1000 american used ,(from canada) How does a new $2000 off the shelf computer from a bestbuy or big box store compare to that old 8 core Mac I had . I need some good input for this