The five slot board with Linux is fine if you're okay with risers, DIY mounts, and creative cooling solutions. It's a personal preference of couse, but I prefer self contained rigs that can be mounted with stock components and without too much fiddling - which helps maintain their re-sale value too. :-)
The reason I mentioned no case is because I plan to use a traditional DIY lego, duplo and K'Nex "case". I already use it for an old server in my cupboard, so the technique is proven...
