Custom water cooling for GPU's

Ok here goes...

Yes, you need a radiator. The specific heat capacity of water is very high compared to other materials and substances and the thermal conductivity of the reservoir is relatively low so the liquid WILL NOT cool off enough especially since the flow rate of these little systems is relatively high. The radiator allows enough heat to be dumped into the air to allow another cycle with low enough liquid temps to suck heat out of your components. The warmer your water is, the slower it will absorb heat from your components and the less total heat it will absord. The bigger the difference in temperatures between your coolant and components, the better heat transfer you will have.

For the pump, it depends what you're looking for. I personally look at pressure head so I can push the liquid through as many components as possible with a single pump. The flow rate on any pump for PC cooling will be fine for almost any custom desktop builder out there, so you want one with high pressure head. I personally went with the DDC with EK performance top.

You can't get too big a reservoir. The lowest temp (with water cooling) you can get your coolant is room temp anyway (second law of thermodynamics) so you won't lose any "cooling capability" by letting your coolant sit in the reservoir a few extra seconds.

You CAN order a universal GPU block, but those don't cool VRAM or VRM so you would want to attach heat sinks to those and make sure there is plenty of airflow in that area. Your best course of action is to buy a full card block if you can find one. If not, like I said, mount heat sinks to your VRM and VRAM so they don't get too hot (depending on your card you may not need to, but better safe than sorry).

Looks like you've got a good list there, just take the question mark off after "radiator"

You may need to buy different mounting hardware if you mount the reservoir outside your case, but you'll have to figure it out depending on your reservoir.

My only tip is to not worry about flow rate, just pressure head. When the flow is constricted when it goes through your blocks it'll speed up (since flow area shrinks, and a water loop is a constant flow system) and your flow rate will be just fine with any of the good pumps out there, make sure you get a higher pressure head pump if you're pushing it through a lot of blocks though.

Better to ask questions now then wish you had later!