What should I get

I know almost nothing about water cooling. I am purchasing an x800 XT to upgrade from my 9800XT. I was woundering what blocks I should get to cool my barton and my GPU. Also my brother (Barrman) said I don't really need to upgrade my northbridge cooling (see my signature). Any suggestions. Also I have a coolmaster, wavemaster Tac-T01, and I want the stuff to fit in my case.

You should really research around and check the stickies, but /spielON.
Base your system aroudn the cooling element. Radiator or heatercore, basically some auto AC Heatercore or a BIM,BIX,BIX2, Swifty 676, etc.

From there you get an idea of your needs.

Ultimate best performance: Storm G4, Maze4GPU, Tygon 1/2" tubing, 2-302 HC or similar dual pass variant, Iwaki mega-pump.

Realistic best performance: Dtek WW, MCP650/D4, Maze4GPU, 2-302 HC or similar dual pass variant, 1/2" Tygon.

Low flow rig of righteous temps: Swiftech 6002, 2-302 or similar dual pass variant, Hydor L30/Mag 3/Via Aqua/ or better pumps if you prefer.

10% antifreeze/ 90% distilled water, perhaps a drop or two of dye

two or four 120mm fans on the HC/rad as you prefer

reservoir or t line, as you prefer, go with t line (bias)

HC knowledge
Basics


Swiftech
DD
D-Tek

CrazyPC
CoolTechnica
Sidewinder
FrozenCPU

The Ubiquitous block comparison chart.
Procooling


Go to it.