Reposted from the Konmari thread at everton's request... I'm all mouth and no trousers with this:
Re more stuff coming in, the trick with the [aspirational room sets in magazines] is there is nothing else there. It's not just the "stuff" in that picture, it's also the empty space where there isn't the pile of school paperwork, argos catalogue, kids' shoes and toys etc etc. A funky box on an otherwise empty bench is appealing. 15 of the same box in that same space, not so much. Part of the appeal is really (arguably) the empty space where the other 14 boxes are not. Buying one funky box will not create the 14 boxes' worth of empty space for you.
For everything you want to buy, balance it up against the empty space it would be filling. Most of the time, wouldn't the room (and your own sense of tranquility, or whatever you're aiming for) be more enhanced by the space than by the thing? That is the theory I'm working on anyway.
Likewise with toys, I try to buy only those whose play value really "earns" the space they take up. You can buy massive plastic castles, enormous toy hoovers etc - whatever you like - but only if you think they will be more played with and loved than some different toy you could put in that space. Do DC need 6 different happyland houses or would two, or even one and a couple of nesting cardboard boxes, do near enough the same job and take up 1/3 of the space? Think what else DC can do with the extra space created - space is such a valuable thing in play.