I've gone back and forth for so many different sets. But after a couple decades I settled on the RID 2000 series. I've "replaced" a number of them with exclusives or related to the original figure; repaint, rename, 3rdparty, or just one that has the same name. That way I get the whole series and still make it unique. I'm on my the path to get a few more, especially that PsycroKnight by PE.
That's such an interesting approach to collecting characters from the series. Always love seeing...well, love for RID. Keep it up! I have Psychro Knight myself and he's great!