After a fatal error message the souped up graphics computer I pieced together is dead. fatal error 0x0 etc.

I want to get the last computer of my life and would prefer some sort of ultimate Mac or a totally secure desktop, but I do not have enough information or insight to know what I should get.

So what kind of affordable computer ($2K - $3K more or less) can I get that will not cause anxiety, migraines, rage or premature death?

I don't need to run Renderman or model hydrodynamics or model the liquid iron uranium core of Earth and its magnetic fluctuations and drag on the crust, but I would like a very powerful and fast graphics card and some next generation capabilities.

What should I get?
Where should I go?
New or used?
Holographic display interface?
Touch screen?
OS? Mac, Windows, both?
lap top + desk top enhancements?

As you see by my questions, I am technologicly out of touch but would like my last puter to be a satisfying one.

help me obi one kenobe.