5d m2 too old? Need a wise answer please.

Your analogy of the car is a poor one - you would most certainly notice a vast difference driving the two. However, I challenge you to place a large print from a 5DII and one of of these later spec cameras side by side and tell the difference.

What photography is all about is the end result - that's it! You are far too hung up about IQ and money to be completely rational here.

I am a retired pro with decades of experience and have had superb results (and still do) from way outdated hardware. What I suggest you do, before making your final decision, is to look at all the lenses available from all the different brands you are considering and look to the future. I cannot stress enough the importance of the glass that you choose. Consider your system as a whole, then decide whether it will be Canon, Nikon or whatever.