A question in general about displaying NTSC through a Mac.

If I understand correctly, the Video Spigot can display NTSC
in a small window as well as capture the data in Quicktime
format.

However, if I want to use a larger window, what are my options?
Perhaps I misunderstood the Video Spigot review...  

Also, I am not interested in Quicktime.  I would merely like to
use my Mac as a television from time to time.  I have a nice
Sony 1430 monitor, and I would like to use it as a second TV
when my wife is watching sitcoms on our regular TV.  

Perhaps some of the video cards for the Mac accept NTSC input?
I have a IIsi, and I am willing to buy a NuBus adapter.

Thanks in advance for any help,