500$ will get you a good kit.
this is a good site for reviews and WC info: http://martinsliquidlab.org/
I just started WCing not too long ago and got an EK loop for my CPU+VRM. The radiator came preflushed so it was a simple case of mounting the blocks, hooking up all the pipes, hot wiring the PSU and running a 1hour leak test.
Somethings to consider most good CPU blocks are within 2C° of each other and as such what you want is high flow rate/looks as temps are more about how well you mount the block.
Quick rundown of what I found out by reading
Alphacool has the cheapest and most effective rads. EK also makes good rads but are a bit more expensive but almost as good as the ACs while being preflushed.
The best block according to all current reviews is the the koolance 380 after that it's a mess as no reviewers agree but supremacy heatkiller cuplex kryos and the 370 are all good blocks.
EK makes the highest flow (biggest internal diameter) compression fittings in any size.
Laing pumps are the best pumps however the high power DDCs can overheat.
Getting a pump top is a good idea as they can greatly improve performance and they always make building simpler
The switch 810 is the best WC case available