[Gooserider]

You want to arrange your plumbing to be as straight up and down as possible, avoid loops that can trap air. Reccomended flow for a setup like yours would be Pump -> rad -> CPU -> GPU (and other blocks) -> res -> pump. I would reccomend making the res as tall as possible maybe cylindrical, with the inlet about 1/4 of the way down from the top, and the outlet at the very bottom. Keep the pump inlet about even with the res outlet, and use an oversize hose for the line between the res and the pump inlet. Have some sort of diffuser on the inlet to slow the water flow down so that the air bubbles have a chance to float up.

The gap between fans and rad should be at least 1", more won't hurt anything as long as the box is sealed tight enough that you don't have any other air leakage. However, you will get some reduction in noise if you can move your fans further inside the box. I would probably put the rad just inside the box with a shroud connecting the fans using perhaps a 3-4" gap, then just have an opening in the back to let the air vent out. If you wanted to get fancy, line the box with some sound absorbent foam and put in a couple of noise baffles.

McMasters has some quick disconnects but be warned that QD fittings are somewhat restrictive, be sure to get the biggest ID ones you can find.

For easy draining, I'd put an extra fitting in the bottom of the res, with a ball valve and hose that can be put in your catch bucket. I'd also put a vent valve up near the highest point in the system so that you can let air in when draining. The drain process would be to turn off the pump, keep the cap on the res, and open the drain and vent valves in that order. Fill process would be to close the valves, fill the res part way, and start the pump, add more water as the air bleeds out and the water level in the res drops.

If you haven't gotten the pump yet, remember that high maximum head numbers will do more for you than high flow rates.

Hope this helps,

Gooserider