gph means squat...what you need to look for is the head (pressure) of the pump. A 1000gph pump with 1ft of head will do you no good in a w/c system compared with a 100gph pump with 7ft of head. Anyhow...i would get around 300gph with good head...most specialty watercooling pumps fit the bill. Some good pond/aquarium pumps (prolly what i would use) are eheim 1250 and the danner mag3, the mag 3 is a good pump for the money...just its best to be submerged because its not sealed all that great. If you wana do a T-line style blead then you should take the shroud off of the pump and seal it with some silicone sealent ( <-only for mag pump, eheim 1250 is a more expensive but nice quiet powerful pump).
For rad, just get a cheepo heatercore. If you wana keep it in your case chevette heatercores work well for this, they are compact enough to fit. If you are looking for a big ass heatercore look to the 70's c30 trucks.
For fans...preferably 2 120mm fans, which you will proably want to run a 7v or use a rheostat of some sort to tune down their rpm. It is a good idea to make a shroud for the fans too, it allows air to flow over all of the rads fins...thus increasing efficiency of the system.
For tubing...1/2 inch id all the way!
For waterblocks...eh read reviews, off the top of my head i dunno who's on top. Been hering quite a bit about the rbx and whitewater, i beleive they offer close performane to eachother.
For gpu block the maze 4 gpu block is pretty good I hear...
For chipset...good air cooling, its not worth hurting your flowrate to add a chipset waterblock.
I think that pretty much covers a diy minus fittings, which im sure you can figure out. Good luck...
If it isn't a P6 then it isn't a processor
110% BX fanboy