Other recommendations
you DONT need computer cases (they will run cooler without cases and you save monies), just keep the rigs somewhere safe from static (not on your carpet or tesla coil) ie. a tabletop
Advantage definately goes to the boards with 4 PCIEx16 slots, as they require less extra equipment (mouse keyboard lcd hdd's ram etc)
But cases are so nice for when you want to move the thing, or sell it without parting it out.
And you got to watch the spacing on the PCIEx16 slots, because I got a board with 4 slots only to find out I could only fit 3 cards in it, as the card were 2 slots wide, so one slot was covered with one of the cards.
Then I have to leave one side of the case open with a fan blowing in it at all times to keep the heat down. Hottest of the three still running at 85 C.