Couldn't have said it better.
Take a look:
http://www.overclockers.com/articles373/
Go down to Bill's test result, and be amazed at Owen Steven's DIY block taking the #3 spot. It even beats the latest Swiftech product.
In other words, unless you want to buy a block, you can make your own, and have it outperform any US made block right now. (end shameless plug
)