The NTSC standard for broadcast TV in the US is 720x480, interlaced. I'm pretty sure there's no progressive that isn't HD. It just looks better on your TV because it's further away and is a low resolution display.
Hauppauge is supposed to be pretty good. High end ATI or nVidia cards are probably good, too. Just Google for reviews and make sure the specifications are adequate, you'll want one with a 10-bit decoder, or better if they have such a thing. You could get an HDTV tuner of course, where you'll get probably 720i or 720p for any broadcast or cable stations that offer HD.
I also recommend
DScaler for viewing TV, regardless of which card you buy. It's advanced and not entirely user friendly, but far more powerful than any other software I've ever used, and provides a much better picture through more advanced deinterlacing. FYI, the "Greedy 2 Frame" deinterlacing method in DScaler is the best overall method as far as I remember. There must be two dozen options, but that's usually the best choice. You may have to fiddle with it a bit before you get it to smoothly play TV without a lot of CPU usage.
Edit: There's also a DScaler 5 0.0.8 alpha that's supposed to be slick.
Bassoon, n. A brazen instrument into which a fool blows out his brains.