At the very least, the OP should talk to someone in person or on the phone about this. There are simply too many possibilities to adequately answer this for a production deployment.

Some questions that I (as a former SysAd) would ask:

1) How many is "many servers"? 10, 100, 1000, 10000?

2) What exactly is "performance for ... multi-cores multi-sockets, high IO & CPU & Memory & Networking"? This basically covers everything ever created. The high-performance for TeraGrid (sci. apps) is very different than E-Trade (financials) and very different from Amazon (e-commerce).

3) Is "low-cost support" $0 and 1 week of searching online forums? Or $100 and a phone call?

4) Do you like "port", "apt", "yum", "emerge", or "make"?

5) Do you need to have multiple versions of the same app available at the same time? E.g., gcc-2.97, gcc-3.2, 3.3.2, and 4.4.1?

6) Did you not know the answer to any of these questions? If so, I highly recommend you hire someone like @davidw says.