I wouldn't have thought it'd add that much weight - there's not going to be much more than a litre or two of water in there, after all. And if you can't lift an extra two kilos, then you're weak, so tough

j/k You could always go for one of those Mach II thingies, if you wanted maximum cooling. Though they're probably as noisy as fans, if not more so...
Back on-topic, though - that's probably the best case mod I've ever seen! Actually original and interesting, rather than a load of leds and fluorescent tubing. Never liked case modding meself, but that is very, very good. Don't like the green/silver one though.