Ok, so I did a price check on what these 980's are worth (not surprisingly, not a whole heap of cash) and decided since they are only 2yr olds, they were going under water. I purchased EK classy blocks and a triple serial connector, now they are just waiting to be put in the/a loop. The i7 (OC to 4.6 @ 1.26v) is on water already in its own loop with a XSPC 240 and 120 radiator. The Classies are not OC'd at this time, but will be slightly when they are on water. I already have several other radiators on hand (all XSPC) 280, 360 and a 140. The case is a Corsair Graphite series 780T and can accommodate a 360 or a 280 in the front, 360 or 280 in the top,  120 or 240 in the bottom and a 120 or 140 in the rear.
So, with that said and the available parts I have:
Which radiator combination shall I use?
Single loop or Double loop?
I am going to attempt rigid tubing on this one, if that fails I'll go with hose (not wanting to but it is what it is)
 
TL;DR
3 Classies and an OC'd i7 4790k, out of the selection of radiators I have on hand best combination  (120, 140, 240, 280, 360)
Single or Dual loop
Maximum cooling minimum fan noise
 
 

Rule of thumb says one 120mm radiator space for each component + 1 extra unit
 
You have 3 GPU + 1 CPU = 4 units +1 extra = 5 x 120 = recommended radiator 360 & 240 
 
 
How thick are your rads ?
 
What fans are you going to use ?
 
Single loop is fine if your pump is good.
 
Dual loop is mostly for show, large systems and extreem OC.
 
I'm running single loop with 2 alphacool 45mm x 360mm with one D5 pump.  This is for my dual EVGA Titan X SC with OC 4790K. 
 
I'm Folding 90% - 99% GPU running 24 x 7 temps at 39 - 40 C in a room 25 C (77F)

howdy2u2
 
EDIT: added link
CoolGTX, STOP editing LOL Just when I think I have answered all the questions and refresh BAM another one!!!!
 I'm OLD and type very slow..........................

Cool GTX Learned that from me

Tag your it
 
Post and go back and proof
 
and go back and add more ...........

yep, it does add up quickly, making a custom loop

That is the worst; you know you have the tool; but, it is just MIA
 
Just updated my loop with some EK Vardar fans they move much more air, they are nice improvement over my entry level Swiftech 120s

 
Show us your handy work with lots of pictures. We like pictures. You could post a mods rig thread if you wanted. Have fun building, that's the best par, I think.

I agree with everything said here. Dual loop is mostly for show or just if you have the room like I do. I ran this same hardware in a single loop and the extended full load temps differences were 5-10c in most situations. So unless your really trying to push the max clocks its negligible. 
 
DDC pumps usually have a higher head pressure then D5's and the one you have should be fine if you go single unless you have a ton of tight bends, 90's or really restirctive blocks on something.
 
I generally will just fit the most amount if radiator I can even when i dont think its needed. Especially if you have them on hand. This will help reduce the peak temps after the loop temp equalizes under load. 
 
 
 
 

WHAT IN THE WORLD IS UP WITH PUTTING PHOTOS IN A THREAD???????
 
A few photos so you know I'm not full of hot air.............
 
See photos below------Blocks
 
And because I wanted to see it in action I hooked up my fan controller: Aquaero 6 PRO
Figuring out how to use the software and set fan ramping and such.......

(numbers for fan % were switching when taking the photo, thus why it looks poor)
 
See photos below--- Temp Sensors
 
 Software sensors are on the MOBO (using OHM/hardware monitoring software) , there are also plug ins for 8 other temperature sensors
 

bcavnaugh
Do you think this would support Koolance Products?

I am not really sure to be honest, I know they have their own flow sensors and a pump designed for this system. As far as fans it will control any of them, PWM or voltage. It does all sorts of things, you change the labels that are displayed. I just hooked it up and was playing around getting used to it.....fumbling around the software and mashing buttons at this point.
 
http://shop.aquacomputer.de/index.php?language=en&  < Link to German website, Most everything is available @ Performance PC though and Amazon

Yagyu_Jubei
If you are already using the aquareo i would stick to Aquacomputer products. They are super simple to use with the aquasuite software giving you all kind of options and full control of everything. I use it ajust my fans according to water temperature and safe data to an excelfile. You can even upload a customized .bmp to use as startup screen in the Aquaero. The remote control is a nice gadget, too.

I have been getting more of the pieces from Aquacomputer, still putting it together though. I agree about the control, this thing will do more than I will use and actually more than I expected. The software at first was a little overwhelming but I have it figured out for the most part. Well, lets say figured out for now for actually controlling fans and such. It's not completely installed since I still have to build my loop, I got side tracked on another P/C project and will then finish this system.