I was sad to hear the Corsair K90 uses MX-Red
Well, how about the Razer BlackWidow Ultimate?
Is there a difference between the three BlackWidow keyboards? Sorry, I've only recently started researching the peripherals.
Well, we have several different types of BlackWidow keyboards. The Razer BlackWidow Ultimate is LED backlit, and uses Cherry MX Blue switches. The Razer BlackWidow Non-Ultimate uses the Cherry MX Blue switches, but isn't LED backlit.
The Razer BlackWidow Ultimate Stealth is much more silent than the Non-Stealth counterpart, featuring Cherry MX Brown switches (which don't make as much noise), and uses a green LED backlit color scheme. The tournament edition is a budget version, and I don't know much about it, honestly.
I'd go for the Stealth Edition, because I'm not to keen on the loud noises of the Cherry MX Blue keys. Cherry MX Brown keys are much more silent, because they deliver tactile feedback, which is, you feel it with your fingers when the switch is activated.
Cherry MX Red and Cherry MX Black don't have the tactile feedback. They're smooth going down when you press them, and they're the most silent of the Cherry MX switches.