I highly recommend reading the reviews on skinnee labs website.
http://skinneelabs.com/ek-supreme-hf.html?page=4
They have reviews for pumps, waterblocks, rads etc.
I'm not an AMD guy... is Opteron the same as G34? If so, the EK Supreme HF blocks will work.
EK-Supreme HF - Full Nickel - CPU Blocks - Blocks
The 450 is the same as a swiftech 655, or more commonly called a D5, just FYI. It is a good pump, but I recommend going with the 450 rather than the 450s. For a few bucks the variable speed control is nice.
There is no need to go with all the same brand equipment if you don't want to, provided everything has G1/4 threads.