EyeTV would probably work, but I'm guessing here that you're going to be able to maximize quality by going with an Analog-DV converter box. You may be familiar with how some MiniDV cameras have a "passthrough" mode where you can feed them an analog input signal and have them spit out a DV stream of that signal, which you can in turn capture with iMovie (or QT Pro).
Well, there are also little breakout boxes that do that without the camera part. I have an OLD Sony one (I'm 99% sure they don't make it anymore) that still works extremely well. In fact, it even has exactly the sort of passthrough you're talking about--I just plug the component outputs into its "input" jacks, put it in Analog In mode, and I get a DV stream coming in to my computer. If I also plug the TV into the "output" jacks, I get an additional passthrough signal that I can watch on TV if I want.
A very quick Google search turned up the "Pyro AV Link" (low end model) as one example for about $160 or so. It doesn't do direct passthrough, so you're either going to need a splitter box (can be found at Radio Shack or just about any big-store AV section) or a TV that has outputs on it (some higher-end ones do).
The advantage of these boxes are that you get a very low-compression DV stream into the computer that iMovie is quite happy to help you edit and recompress into any format you want, and you needn't worry about drivers at all--since it's just a DV stream there are no drivers, it's just treated like a camera input.
The downside compared to, say, EyeTV is that it won't work particularly well for watching TV on your Mac, and doesn't double as a DVR. But if all you're looking to do is digitize video and want to do it without spending the money on a pro capture card, this is probably your highest quality option.
