I use Aquacomputer parts.
I have a low flow system and their CPU coolers like the double impact work very well to cool my Q9550 at a 0.3 liters per minute rate. I also use an Aquagratix for my 4870x2 and it works quite well. The double impact had a high resistance so it's a no go if you have high flow systems, but the HD or the EVO look really good imho.
Sorry, no experience with i7 so no idea about the value this block would have in comparison with other vendors.