The thing about modding is that nothing is standard. But as reggie50 says, some cases are more readily suited to it than others. Anything with two to three 120mm fan holes side-by-side will more easily accommodate a two or three fan radiator. Which regardles of what you want to cool is about the size you are looking at. You can watercool about 230W worth of components on a single fan radiator, but it does not give you much wiggle room for future upgrading. Pumps: anything Eheim or Laing. Radiator: they are all more or less the same. Black Ice is OK, Thermochill has the edge, Aqua Computer's modular system is pricey but versatile. Tubing: Tygon is the de facto standard, but some people prefer Clearflex because it is cheaper and almost as good. Don't get drawn into the age-old argument about tube diameter. Anything from 8mm ID to 12.5mm (1/2") ID performs pretty much the same. I find 10mm a good compromise between performance and routability (thin tubes bend in tighter curves without kinking). Barbs: they are all the same. Pick whatever suits your needs. There is a huge choice in angled and swivelling barbs nowadays. Cable ties: any plastic one's will do. I prefer stainless steel worm drive clamps but that's just me. Blocks: read the reviews... Most perform on a par but a few have the edge over others.
That eBay seller is... priceless. They're a shyster using images that they don't have the rights to, all with the intent of hucking what's likely to be a poorly put together system using a bone stock Thermatake Watercooling Kit. Plus, take a look at some of their other auctions. a "4.8GHz" i3 CPU? Where'd he find that, under the crack pipe?
Pumps I have seen have vast price differences. Laing are quite costly, what about Phobya or compacts ones say between 20-35 pounds? Could a single radiator suffice for sempron or dual / quad core cooling?
Aquatuning are good, they have a sub forum on here, but the delivery times can take over a week at times (as it has to be shipped from Germany). The other sites I use are Specialtech and WatercoolingUK, both UK based companies. The Liang pumps have gone way up in price recently, but are well worth it. Those Phobia pumps are good for simple loops (from what I've been told). Your other option is a XSPC all in one bay res/pump, it's also good for simple loops and saves on space and money. (Just to add a simple loop is just a CPU loop, with a 120 or 240 radiator)
A single 120mm would probably suffice for a single/dual core CPU, 240mm is the minimum would should be looking at though really. Sent from my HTC HD2 using Tapatalk