I'm pretty sure I can shutdown, install 4 RAM stick and restart a computer in 3 minutes or less. That's not a significant downtime.
Which Prolimatech are you eyeing? The old but very decent Megahalems is still sold at a few places, but it's becoming rarer and rarer. The new SuperMega beats it by a small margin, but is 10-15$ more. The Armageddon isn't worth it. There's better for the same price. Like a Scythe Mugen-3 or Thermalright HR-02 Macho. There's also the Thermalright True Spirit with a TY-140 fan that makes a cheap, but very effective combo.
I cool my i7 2600K with a Xigmatek GAIA S1283 with a Scythe 120mm PWM-controled fan. Never goes above 60C and while I can hear it (my room is otherwise completely silent, could almost serve as an anecdotic chamber), it is not disturbing at all.