For the GPU blocks the challenge is to get block to fit in a reasonable space without killing flow rates with 90s/elbows. I like designs something like this:
http://shop180.eoa.de/cgi-bin/shop.d...htm&verteilt=1
http://www.aqua-computer-systeme.de/content/kuehler.htm
esp if barbs angle a bit to clear ramsinks on cards. The Innovatek GPU cooler I had did this well too.