If you can find a group which make blocks (mips or ek are most likely) it'll be around £80 for the board.
Graphics card you have the option of core only or full cover, the former is cheaper and dumps less heat into the loop, and can be used on multiple different cards, but the latter cools the ram and other bits as well. I prefer full cover blocks.
The laing D5 or ddc is the pump you want really, but it will cost more than the ocz. Things are a lot cheaper second hand, and radiators/blocks don't really change with time. I have a new and a second hand 120 radiator, no longer have any idea which is which.
Watercooling in the antec 900 will be interesting. You need to find places to fit radiators, and the 900 doesn't really lend itself to this. How do you feel about an external radiator, say built into or sitting on top of a desk?
