The "super high grade ultra durable" rack mount power supplies are nothing of the kind, I've got a pile of fried power supplies and they all tend to be redundant ones. Interestingly, I find we get few failures around here just buying halfway decent regular power supplies. Some of our ESXi nodes have the fantastic (but expensive) Kingwin STR-500 fanless 500W supply, running a Supermicro X9SCM-F board, 32GB RAM, and a Xeon E3-1230 for about 45 watts idle consumption, 90-100 under full load, or something like that.
The real enemy of computers is heat, and so one of the things we did with these ESXi nodes was to carefully look for the ideal parts. We have a small pile of 4U rackmount cases that are really nice and generic. Inside, two 4-wire 120mm fans are the exclusive cooling for the system, uses less power and keeps heat down. The power supply has no fan and is rated up to 500W, but we run at 10-20% of that, so cooling it isn't an issue. We have a massive passive cooler on the CPU, and these things wind up having the interesting property that they never rev up their fans (and actually had to have their BMC values tweaked down to reflect that) and run just about silent. I never expected the switches at the top of a rack to make more racket than the servers in the rack. ;-)
Now, I'm going to impart a little wisdom from years of experience. noobsauce80 and louisk are right, in a certain way, that many of the rack servers that are out there are not designed with power efficiency as a consideration. AT ALL. That's not at all because the servers are rackmount, but rather because IT departments like to buy servers big enough to make sure "it's never a problem" and service providers in data centers don't like paying $1500/month per rack and then not filling them with as much density as possible. So in both cases there's a bit of incentive for manufacturers to place as much power as they can into a server, and those models sell QUITE well. But you can - if you know what to look for - find prebuilt energy-efficient rackmount servers. And you can - if you know how to do it - build them yourself.
If you want to build your own, and are familiar with building desktop/tower? Here's the big secret. Many of the 4U chassis would be nearly indistinguishable from a standard tower on the inside. You lay them out similarly, you design them similarly, you wire them similarly. You can choose your parts for energy efficiency. SO USE A 4U CHASSIS. I haven't actually seen one of the Norco's, but those look kind of promising for inexpensive builds.