You didn't mention a budget.
I'd get the video card and power supply, the GTX 660 is gonna be the weak link but if it's the stock Dell/Alienware power supply I'd trust it about as far as my dog could throw it. You can get good power supplies pretty cheap, e.g. the
BitFenix Whisper M, about which I've seen stellar reviews, and something like an RX 480 is a relatively inexpensive drop-in upgrade that'll really kick graphics performance up high compared to the GTX 660.
All depends on budget though. You can do more with a higher budget ceiling or pinch a penny or two if necessary.