As you've got a 600t that does somewhat limit what you can do, considering those 580GTXs run hot. I cool a pair of 5970s with a quad radiator, which is going to be roughly what you need for the 580s. I guess you might be able to get it down to a thick 360mm rad but it might be a bit too warm. With regards to the CPU, I don't know what voltage you are running (I'm guessing quite high, which can damage the chips), but you will want a dual radiator for that.
You can go for a dual loop or single loop, as you have a pair of very toasty graphics chips, the CPU is going to be less tolerant to the heat from those, so you will probably want two loops. Pumpwise you should look at the DDC 18W (or a pair of them) as they are pretty reliable and have a good range of tops. The resevoir top is always a good bet unless you want to put in a different kind of resevoir. A silver coil acts as a kill coil, it prevents algae from growing in your loop. Alternatives include premixed solutions which generally have algaecide in them or alternatively using a fair bit of antifreeze in the loop.
Final point, please ensure your post is checked through for spelling, grammar etc. It makes replying uneccessarily difficult.
