UPDATE: One motherboard later, and I'm back in business - SLIed 670s and a Cooler Master Hyper 212 EVO.
The install was pretty smooth, thanks to YouTube videos showing the process. I used ArtiClean1 and 2 to clean off the CPU top, and ArticSilver5 for paste, and the backplate and mount were no problem.
The only minor hitches was the first bootup with the new motherboard, where it hangs for a couple seconds, shuts down and restarts.
I think I motherboards do that the first time they post? Also, I had to re-activate Windows, which was a somewhat lengthy but smooth and easy automated phone process. Lastly, I was getting some red flashing/flickering in games using SLI - a quick Google search revealed the issue to be the SLI cable not seated properly, which was true.
Noise level at idle isn't much different then the stock, but I can tell it's going to be much quieter when it heats up because the stock fan made a loud "whir" sound when first powering on, but I don't think I've heard the EVO spin loudly yet.
As for the temps - not ground-breaking, but a nice improvement. Before I was lucky to be idling in the very high 30s, usually in the low 40s. Now I'm at the mid to uppers 30s idle. But the good news is when I push it in intensive games temps haven't gone above low to mid 50s, which is quite an improvement. I used to be seeing 70s with stock cooling, so I'm pretty happy with it. Now after it settles in I might try to OC that "K" CPU.
So, bummer I had to buy a new motherboard, but I learned a lesson and feel the system is better off now than it was before, so it's all good.
Here's a pic of the install in progress: