if you have a ddr4 board you need ddr4 ram i recommend http://www.newegg.com/Product/Product.aspx?Item=N82E16820231888&cm_re=ddr4-_-20-231-888-_-Product and i would also get a 980 ti
its about 200$ above your budget but in cad it is really hard to do that budget and your can pick what ever os u want i left that to you
http://ca.pcpartpicker.com/p/VWFrZL
the dns severs have nothing to do with that it will still be on your router and will probabbly continiue infecting everything thats on your network
calll your internet provider for the sake of your devices