I dont think you need to go that high.
Pump(s) + res - ~100$
Radiator(s) - ~100$
CPU block ~70$
GPU Core blocks ~50$ a piece
Tubing / fittings - highly variable, you can spend a ton on these but if you go for budget then you can get away with approx 30 - 40 $
So - about 400 $ altogether for a loop which can handle CPU + 2x GPU's. I would prefer GPU core blocks as these can be reused unlike the full cover blocks that fit only the specific model and when you upgrade you have 100$ paperweight per card and need to spend again.
CPU - http://www.aquatuning.us/product_info.php/info/p13551_EK-Water-Blocks-EK-Supremacy---Acetal--1156-1155-1oe-2011-AM2-AM3-939-XEON-.html
GPU - http://www.aquatuning.us/product_info.php/info/p14121_EK-Water-Blocks-EK-VGA-Supremacy---Acetal.html
radiator - http://www.aquatuning.us/product_info.php/info/p2050_Xtreme-NOVA-1080-Radiator.html
pumps/res - http://www.aquatuning.us/product_info.php/info/p13016_Alphacool-DC-LT-Ceramic---12V-DC-Pro-AGB.html
(its a bit weak for pushing 3 blocks so 2 pumps, need res only on the first one)
tubing - http://www.aquatuning.us/product_info.php/info/p745_tubing-PUR-10-8mm--5-16-ID--clear.html
(couple of meters will be enough)
fittings - http://www.aquatuning.us/product_info.php/info/p4836_10-8mm--8x1mm--compression-fitting--G1-4---black-nickel.html
- need altogehter 12 fittings, 2 for each blocks and 2 per pump and 2 per rad. If its straight, 45 or 90 degree depends on how you plan to put stuff. If you mount the rad externally then you can either route tubing straight to the rad through the holes in the back or, if you prefer use bulkheads, in which case add 4 fittings + 2 bulkheads.
Or, you can start with a kit and add GPU blocks - http://www.aquatuning.us/product_info.php/info/p13670_Alphacool-NexXxoS-Cool-Answer-360-LT-ST---kit.html
- note that I personally dont like that res they have in that kit so I would dump that and order instead the separate plexi tops for the pumps and either the integrated small res or separate round tube res.
Edit: I kinda like that particular radiator, as its pretty damn good price per surface area and its substantial overkill size wise so I would expect the radiator would be adequate for whatever system and thermal load you throw at it. It is also relatively easy to mount externally - just bolt it to the sidepanel behind motherboard tray - thats what I did:
build log for that system can be found at: http://www.overclock.net/t/1262095/soliton-dispenser-an-atx-portable-watercooled-case-with-external-9x120mm-radEdited by Carniflex - 10/29/12 at 1:10am