Weelll... after the first shock I'm not sure that this is a bad idea. The bigger the fan, the lower the rpm, right? And dumping the air outside the case is of course a good idea.
As for sizes, and IMO:
In the beginning, bigger heatsinks were kinda cool (in a style sense, and provided a nerdy disposition). Then they got so big that it stopped being cool and was just ridiculous. But this thing, ah, this thing has continued all the way through the ridiculous zone and emerged on the other side, being cool again! 8)