Choosing a Graphics Card

Hey so I'm planning on building a computer to allocate to a nice virtual lab and to play around with hacking some. I'm planning on building a $1000-$1200 set up with 16 gb ram an i7 4 ghz or greater processor something along those lines. The one thing I don't know about is the graphics card. I definitely want one so that the processor can use all of its power but I don't know how nice of one I really need since its not gonna be a gaming computer. Also should I keep in mind that I may want to overclock it and use it for password cracking or what not. Please let me know of your thoughts. Thanks!