First of all let me welcome you to your new addiction lol I have a blast mining but it does take a lot of time to get it all set up, but the extra income is worth it. This is just the beginning, you'll be wanting to expand soon. That 1200 watts PSU is overkill, the a max power of of the 1060 is 150 you can downclock them to 100 or even less just depends on the card and you dialing them in. so your 450 watt should be fine for 3 cards just make sure you have enough power connections. I run 4 GTX 1080 it's off a 1200 PSU. You'll probably want to order some PCIe Risers, you can space out your cards more so they'll stay cooler. you can pretty much use anything for a case there's actually a lot of videos on YouTube of people using milk crates or you can build out of angle aluminum. good luck man let me know if you have anymore questions....have fun