Cokin P Filter Sytem

After collecting a bunch of filters all these while I've decided to get a cokin P series filter holder. The difference between this and the usual screw on filters is that you get to slip in a piece of plastic into the holder. The cokin filters don't excite me too much, as the optical quality is so-so, but what is interesting is when I get my hands on the next purchase, that's a bunch of graduated ND filters from one of the more specialized filter companies. Singh-Ray is one of them, but the prices of one of their ND filters are quiet high for something you don't use for most photographic occassions.