Dual Loop versus Single, the facts

[Church]

My thoughts:
to get smartly relatively cheap budget with better noise profile cooling: Air, and only air. Top cooler like thermalright archon or silver arrow/phanteks ph-tc14pe/zalman cnps12x and likes + something of 3rd party air cooling for gpu-s with big rads nad more & bigger fans on them (i'm not competent which are best here). +Maybe few extra case fans to enhance overall airflow. Nothing will beat air on relative simplicity/reliability and by price/performance.
next stage: still top air on cpu, but contrary to what many do (LC only for cpu), small-rad LC for gpu only. As TDP of top gpu-s are more then that for cpu-s, but their cooling solutions have to fit in much more constrained limits in 1-3 slots, thus gpu-s should be prime candidates for LC instead of CPU-s to get noise and temps down. +Higher overclocks of gpu will net more FPS then higher overclocks of cpu, which probably matters more for majority of us consisting from gamers instead of crunchers/folders. Even single 120mm rad section per top gpu with even high deltas will bring temps and noise probably on par or better then top 3rd party air cooling solutions, and much much more so then stock cooling.
next stage: LC all major heat dissipating components in single loop. Here i take into account original findings of Gabe of pros and cons of single vs dual loop. Probably one will have to add relatively more rads though, as acceptable high deltas for gpu-s may hurt CPU temps/overclocks, but still overall single loop wins. I also did mention "major heat dissipating" not "major" components, as cooling 7W chipset/RAM/or HDD with LC is everything but smart gains/cost wise. Yes, many do (mostly for bling so), but for smart spending those should be left out.
instead of next stage (with big pile of rads of whatever configuration (two MoRa3-s, 3 quads or whatever ), LC everything, uber controlling solutions) i'd probably would start to consider single phase cooling instead. Costs get similar, but cooling not. Getting down further below 5C delta will cost same, but will net worse temps then extreme cooling, so why go for it? So while extremities like NaeKuh's build is interesting experiment, it simply is unwise as to what you get relative to investments, as there are better alternatives available.
next stage .. even more extreme coolings? Heck, no. NOT for everyone. NOT wise in any reasonable way to actually using PC to do some job. Clustering/more PCs will use less electricity/compute better then these, made for select uber-minority for whom PC is only for momentary max overclock, not actual use. So imho it should be left out of scope for 99.9% of majority of users.