I'll try to answer some of your questions...
- Is the Coolermaster case above the best one for watercooling?
In my opinion, there is no "best case" for watercooling. A good starting point would be any case which offers good quitening aspects (for example the tried and tested Anted P182): the idea is to keep things quiet which are inside the case, and because watercooling transports the heat outside the case, it should be fairly easy to do so.
- Can the case accept a three (triple) 120mm fan radiator at the top WITHOUT case mods?
Assuming you mount the radiator outside the case, you still need to mount it... A few drill holes will be needed - some moddinjg will always be necessary.
The top of this case is curved, usually a flat top is easier to mount the radiator.
- Is there enough room to fit all the watercooling components in the case (might use a t-line rather than reservoir).
Any large case should be able to accomodate for all the components, and this is a large case indeed.
Check some picture threads of other popular forums to see what things look like in practice.
- Is watercooling two gfx cards in SLI a pain in the A*$E? Should I just stick to one? I've heard people say that you should go for a second separate loop for the GPUs - is this strictly necessary if your w/c setup is good enough (and your fan/rad combo sufficient)?
Adding another GPU will add about... 150W ? to the heat to be dissipated (depending on the card), which will obviously add to the noise generated by the fans to keep things cool enough.
My take on 2 loops, but I don't know if it holds: CPU's like low temperatures, and their TDP is not as high as a GPU's TDP. Adding a GPU to a CPU in the same loop will add a significant amount of heat, therefor the average water temp will go up quite a bit, which is "bad" for the CPU. Splitting them into 2 seperate loops: the CPU with lower TDP has the benefit of being fed cooler water, while the GPU with higher TDP has higher water temperature, but the GPU can handle higher temps better.
- The ASUS X58 mobos seem to have a northbridge HS already attached (some with heat pipes joining other components etc.) How on earth do I (or even should I?) go about w/c that? (Without breaking the mobo!) Should I just rely on v quiet case fans to take that heat away? (Bear in mind I want to o/c the i7 920 CPU to about 3.2 - 3.6GHz...)
Don't. All WC cases still need airflow going through them to ensure these kind of parts still get cooled (NB, RAM, VRM). These parts can be sufficiently cooled (to say the least) by a moderate amount of airflow. The niftier motherboard come with good heatsinks to cool these parts, and most even with heatpipes to transport heat to other parts, balancing to overall heat.
- Is it easy (and relatively safe!) to remove stock-attached HSF assemblies from gfx cards? Should I just get a gfx card with water block already attached? (Can you suggest any good ones?
Very safe. There are a lot of reviews on aftermarket coolers (aircooled or watercooled doesn't matter in this case). In almost all cases, the warranty expires once you remove the stock cooling (but then again, you can always put it back, who will notice). GPU's with already attached waterblocks are expensive, with comparable (or sometimes less) performance. I like the full water blocks, but some people like the GPU blocks in combination with memory heatsinks (again, enough case ventilation is needed).
The only thing that might be scary is, removing something from a 400 bucks piece of hardware. Remove all screws (check the back slot too), the "hardest" part is to remove the heatsink from the PCB once all the screws are gone - just keep twisting the heatsink from the PCB, mostly they will move only by a few millimeters (don't pull!) and after a few twists, both will pop off from eachother.
- Thinking of spot-cooling the memory - is there anything else I should spot cool (I guess the NB and attached heatpipe fins might be worth spot cooling)?
Usually, no need for spot cooling. Only need a rear case fan at 600-800 RPM.
- Could you tell me what the best CPU block, GPU block, and pump combination would be for my system? I want to use nice 1/2" (ID?) tubing, but am worried that the components won't have the right barb sizes.
There are so many components to choose from... Make sure the tubing is correct for the waterblocks, or be prepared to use adaptors (not necessarily a bad thing). Depending on what type of blocks you're going to use (high or low resistance), the pump needs to be adjusted. High flow/head pumps are more powerful but also more noisy.
- Is there any way that you could spec the components (above) ensuring they are all made of the same metal to avoid galvanic corrosion? (This includes the inside of the rad etc.) I've seen some blocks that are made of nickle, some al, some copper - argh!
Copper is the most popular metal. All manufacturers should tell which material they use, if they don't, don't take the chance.
- What is the best (circa 1000W) "silent" (just low noise will do!) PSU?
That is quite massive...http://www.xbitlabs.com/articles/coolers/display/system-wattage.html
Lots of good PSU's from the http://www.silentpcreview.com/Recommended_PSUs
- When the system is plumbed together and you are leak-testing it for 24hrs - they say you should not have the mobo in place (of course!) to avoid water damage. However, when you have finished the testing and need to connect all the water blocks (CPU and GPU(s) ) back onto their respective components - how on Earth do you do that in-place?! I find putting a newly thermal-pasted HSF assembly onto a CPU seated in a mobo sitting on my desk problematic enough without having to do this inside a case (and sideways)! Is there a trick to it, or am I missing something?
I always found this funny as well. I only WC my GPU, so that's fairly easy: test it, then just push the GPU in the slot. I don't know how others do this without disconnecting some parts of the loop.
- Lastly (sorry!) - I'd like to use some nice Tygon 1/2" ID tubing for the system. Can any1 tell me where I can get this in the UK? Also, I presume some softer silicon tubing would be useful either side of the in-line pump (for silence)?
Noise from the pump isn't transmitted through the tubing, you need to decouple the pump from the case, using soft foam to rest it on, or perhaps suspend it using elastic cord.
Good luck (from no expert).