The swiftech 320s cool well within the same area that a thermochill or feser will and cost half as much though. There really is no reason to pay double the amount for 1C. A 280 on its own loop is going to run out of voltage long before it runs out of cooling from a swiftech 320. Same with the i7. My entire setup cost me somewhere around 450 for both loops.
Pumps 85 x2
Rads 55 x2
20ft of masterklear = 15$
The biggest cost is going to be waterblocks for the video cards. Full cover blocks for the 280 will run you around 120 per block, or you can go with a gpu only block and use ramsinks, which will run you somewhere around 60-70 per card depending on the block and ramsinks. Personally i ran 2 dangerden maze5 gpu blocks on my 4870s and they are excellent blocks for only 40 bucks. IF i decide to jump up to 285's i'll probably reuse my mazes.
Another thing you are probably going to want to look into is finding a case that can fit all of this stuff in it. IF you are looking to go all out i suggest checking out MountainMods.com
as their cases are prefitted to fit radiators.