If I were to make a good gun from scratch I would get a G&P Vlotr or Noveske body, Put in one of their 9mm shells in with SHS gears, high speed or high torque motor, all the normal extras, An aluminum toothed piston, I'd have to research but SRC make excellent pistons and piston heads, cheap too, Either a stock marui hop up unit or an actual G&P one and then a TBB of your choice.
Oh and if you wanted cheap get a Cheap metal body and put in a full SRC gearbox, G&P hop up unit (Very cheap on ebay) Madbull barrel and a high speed motor, oh with a 9.6v or Lipo. -Actually thats what I'm running in my M4
In his defense, I have heard pretty good things from guys that have used the Combat Machines. That said, in regard to your list, just because something says "high performance" or "precision" doesn't mean it is, and at the very least dont get that barrel...
If you want to pay the price I'd go for a systema motor, high torque and speed. slow motors can give away your position. I would also change the barrel to a 6.03 prommy. much better quality, but again, expensive. make sure you have a good piston as well if you're using an M140.