I have something like 2tb on my laptop. The files are only around 500mb max if you don't get the HD. This first episode of GoT was something like 1.3gb, but it's only in 720p.
The problem with downloading the HD 720p versions is that they're encoded to a .mkv file. Since I stream my video to my 360 to watch stuff, instead of using an hdmi, dual-monitor setup, I have to have them in .mp4. This blows, because all you get is the widescreen analog, which is somewhere around 360p. The audio quality of the torrents I download is awesome. If you play around with it, you can fudge a .mp4 with 720p and 5-channel audio which is only 900mb. Requires some video editing software. Needless to say, with a 12 episode bunch like this, you're gonna need at least 12-14gb of space.