Hardware for stable web service
Hardware power is never enough. But should we buy new one. I think the best way is to squeeze out the most from what you got already. Since 1995 I’ve touched almost well know brand IBM, HP and Dell, from low and to enterprise, and I can say all of the are reliable and easy to mange, but … until you don’t pay for them. So if you a start-up counting each pence in your pocket than you should choose the chip, easy upgradeable, easy recoverable hardware. As the “Automatism theory” says that you can build a reliable system if you use many unreliable components, means you can follow it as a mantra an build your rock solid solution.
At present moment I see no benefit of using expensive cluster build by some well known brand, so I will share with you how to do this efficiently with minimum spending. Hope that 3 companies above will not assassinate me for this information 
*This article will be extended soon.
Currently the alternative between own-built system and brand server is SuperMicro chassis withr redundant power supplies. They are not expensive, they are rack-mounted, the are compatible with non-server components, and redundant power supplies gives you corporate level stability. You can buy your own IPMI or use Motherboard with built-in IPMI.