- blurry interlaced picture with HD5xxx and newer (though some people might like it)
That's not a helpful way of describing the phenomenon. The 5000-series cards and above have flicker-filtering, and the higher-end in each series the card is, the heavier that filtering seems to be - though that might need confirmation. They also deliver much brighter colours in general as you go upward. BUT, the heavier the flicker-filtering of the card, the more the individual pixels are blurred. This means a 240p picture is also blurred slightly. However, it will make a 480i picture look much clearer because some sets flicker like crazy, though some are almost ok. So the pixels are smeared a bit, but the lack of flicker means you can actually see them.
It's worth checking out whether you'll be using a lot of 480i, and how much flicker your CRT has. I use 480i a lot (Grid, outrun2, model2, supermodel, demul) and my PVM-2730's flicker really terribly. My 6870 and 6950 are amazing, really colourful and clear with almost no flicker, whereas a sapphire 4890 was flickery and halfway dull. My 4350 was really dull though, so it's better than that. I also have a 20" arcade tube with a 1983 chassis that hardly flickers at all, but the amount of blurring produced at 240p by the flicker-filter isn't too bad, and the upgraded colours are so nice I'm probably not going back.
In both the above examples the tubes are relatively low TVL though, so on tubes with a finer dot-pitch (higher clarity tubes like on later PVMs or mb later Nanaos) the blurring effect might be more noticeable.