Are these all compatible?

I would personally suggest 1.) Building your own computer, because you can save money and get what you want and get better parts, and 2.) not getting parts from Best Buy. A computer, yes, but a PSU and GPU can be purchased from a place like Newegg.com for cheaper. Regardless, if you go through Best Buy, purchase the desktop and GPU first, and see if it has sufficient connections/power. If not, that corsair psu will be more then sufficient. Hope this helps!!!