Depending on your cable provider you will get sd channels with just cable to tv. Usually HD channels need a hd box, assuming the tv is 720p or 1080i. you will get HD channels. If you don't want to pay for cable, an over the air HD antenna will get you digital/HD channels for free depending where you live.
Media room- LG 4K OLED EG9600, Pioneer Elite VSX-90, Samsung 4K K8500, Klipsch Gallery G28's, Klipsch Sub 12, Klipsch RS-52 II, HTPC, Optik HD cable
Living room- Sony 4K 79XBRX900B, Onkyo RC-360,HTPC,Klipsch Reference R-62II,Rc52II,PS4
Gaming room -Panasonic ST60, PS3, Wii