Ooh, nice one!

I think I got it all sorted now, then

I've revised my design from that above:
Antec P160 (case) and window
Cooler Master Aerogate 2
Swiftech MCP600
DangerDen Heater Core (own shroud)
120mm Vantec Stealth Case Fan x 2
Danger Den Reservoir
Danger Den RBX
Danger Den Maze 3 (Radeon GPU)
Danger Den Z
10 foot Danger Den Hose
4 Packs of 4 Worm Drive Hose Clips
50ml Water Wetter
OCZ BGA Copper Ram Heatsinks (for GPU)
Dark Blue UV Additive
3 Light Blue Cold Cathodes
In the below format:
The MCP600 draws from the Danger Den res right next to it. It pumps to the Danger Den RBX. This splits the water to a parallel system pumping to both the Danger Den Maze 4 GPU and the Danger Den Z Block NB. These are recombined using the Y splitter from the RBX. This then goes to the Heater Core and back to the Danger Den res.
The pump and res are at the bottom of the case to reduce chance of errors in case of leakage

. The Heater Core is placed at the top with a home-made shroud and a quiet 180mm fan using a hand-made blow-hole.
The tubing isn't exact. I'd probably reverse the Heater Core by 180 deg. so the hose comes down easier, and the bends will be larger so no kinking. I'll shove the cathode's somewhere once I've seen how much room I have left etc. and how much is shown by the window.
Sound all correct to you? I'll prob order the case soon cause it looks like it's low in stock at most places. That'll help with planning things better!