I bought mine second hand with the 200g gold heatsink and an xice 9800 waterblock
As far as I know tekheads are the only shop in the uk the sell the koolance exos. Tekheads and extreme cooling are the same company, just if you order from extreme cooling you get free p&P.
I havent heard about the new corsair hydrocool yet it seems interesting if its much better than the old model, I thought the old one was a bit rubbish compared to the exos
The 200g koolance waterblock is very good and I cant imagine the new one knocking off anything more than 1C