If I am to lay the motherboard horizontal, the case fans will have to go a bit differently.
Keep in mind, each diagram is a bird eye view. The dashes are to try and keep the letters in line.
(B = Back of motherboard, IO ports etc., M = Motherboard laying horizontal, F = Fan, P = Power Supply, H = Hard Drives, O = Optical Drives)
Though, it will be much easier to have the power supply as such (below) and run the wires (from the power supply) through that particular side of the motherboard as it will easily reach the places they need to go. The problem with this is, that the power supply is now in the way of a fan.
So, it would be better to have the power supply in front, with the hard drives and optical drives placed on the top, but at the rear of the motherboard box and possibly sitting on the power supply or the box that the power supply may be in.
Then the final complication, don't I want the back of the motherboard to face away from me? But now I have a power supply with a power cord coming out at the front! It is hideous!!! Well, my answer to that is to have the side or back of the setup facing towards myself (where I am sitting, etc.) With the back facing towards me, the benefit is that I have easy access to the ports, but the downside is I still have cables and stuff that look nasty coming out of it (but better than a huge power cord in my opinion.) The side would be the prettiest, but would be bland in my opinion. The optical drives and hard drive boxes (of identical size, theoretically) would of course be facing myself at all times.
I'll see what I can do
New thoughts; birds eye view as usual, with this key: B = Back of motherboard, M = Motherboard (Laying Horizontal), F = Fan, P = Power Supply, H = Hard Drives, O = Optical Drives, N = Monitor, and D = Dockery (as in, where I am sitting.)
Now to illustrate where the hard drive box and optical drive box will be (remember, the fans are still in the same position, I just don't have room to add them in this "drawing." Now imagine all the M's constitute one motherboard.
Ahh... it's all planned out