Nope.. Just an HD compatible video card will work.
Typically video cards have DVI (Digital Video Interface) ports on them.
If you buy a monitor or a HDTV. Find out what ports are on the monitor or HDTV.
Typically monitors have DVI ports. HDTV's also have DVI ports most of the time... If the HDTV does not have a DVI port you can buy a cable which will convert DVI (from your computer's video card) to HDMI (on your HDTV). It's a cheap cable/adapter as long as you buy it from the right place. Most local stores are a ripoff, I reccomend you buy it online.