Buying Servers

I don't get the chance to buy servers often so when I do I get overwhelmed with the details. So much so that I had to revisit what I had already spec'd. Do I need a split backplane? Does anyone need a split backplane? What the hell is a split backplane? Well I figured it out. The answer is no; the few dozen people at my organization don't hit the Exchange or File servers hard enough to warrant all that fanciness. I get the split backplane anyway but don't need to use the functionality as I'm sticking with RAID 5+1 only. Of course if I get it wrong it could get expensive but buying servers has never been rocket science considering the basic requirements for the non-profits I've worked for.

Anyone ever have a nightmare situation because they chose the wrong specs for a server? I imagine it would be a little hard to get it completely wrong, however, that thinking could also be the road to disaster.