I just got done watercooling my SFF rig both GPU and CPU on the same loop. As is the story with most I could never just finish my PC, I kept upgrading which, in turn, required other upgrades and now I am to the point where I think I'll just have to start all over. I started with a little Silverstone Sugo 5 with an HD5670 and an AMD 760K which worked good on medium settings. Got some money and upgraded to a GTX 650Ti Boost and 8Gb of 1600 RAM. Wanted to overclock the 760K but in that SFF rig with only one fan I overheated too easy so cut the front out of the case and shoehorned in a Corsair H55 AIO watercooler, this worked great and everything was copacetic until some newer games started coming out and I couldn't hit max settings anymore and I ran out of storage with only enough room in the case for one 3.5" drive and one 2.5". Sooo....bought a new Silverstone ML-07, which is just a cheaper version of the Raven RVZ-01. Good news is had enough room now for three 2.5" drives and one 3.5". Also was able to fit my watercooler in it with the Ti Boost. But I got the bug to upgrade again and bought a R9-280X Windforce and low and behold it fit in my case but I had to nix the watercooler. Well I had heard the AMD cards like to run hot but this one was running too hot for my little SFF case and I was having a hard time finding a good CPU cooler that would fit the space I had sooo. I bought a bunch of custom water loop stuff and started planning out a loop. After getting my pump, reservoir, and some tubing I realized nobody made a GPU block for my Gigabyte Windforce card. Looked everywhere and all I could find was the universal fit type that just cover the GPU and leave the VRAM and other stuff out to fry. Finally found something from Alphacool but it really wasn't a full coverage block. Threw it all in my case with one 240mm radiator and one 120mm and it now runs at barely reasonable temps. I know my problem is I just don't have the room to fit the sort of fans that are needed to cool the radiators so I am now looking into another new case that I can at least throw some watercooling at the CPU and just have enough room for proper ventilation around the GPU. Long story LONG.. if you're looking at a custom water loop-plan and measure two or three times first and then buy all your fittings instead of just buying them piecemeal as you figure out how you're going to route your lines. If you have a large case with plenty of air flow and you aren't shooting for any overclock records there really is no need to do a custom loop for your CPU and GPU. If you just want something that looks cool, is completely unique to your rig, and money is no object, then by all means go for it. If you really want to overclock and want both your GPU and your CPU to stay super chilly the general rule of thumb I found online is AT LEAST a 120mm radiator for each component you're going to cool. You also have to take into account the space you have, the thickness of the radiator(s), and whether you're going to run a push, pull, or combination fan system. As in my case if I were to have the room for more than a 12mm thick fan I would be running at probably around 30 degrees at full load with my 760K overclocked to 4.3Ghz and the GPU overclocked to 1550. Hope this helps and sorry for the novel.