VegetaCreeper
I have an EVGA GTX 1080ti Founders Edition in the mail to my house right now.  My question is this...
 
With the reference 1080ti founders cooler, is the load decibels unbearable? I do have good airflow in my case with 3x120mm fans in the front.  My case uses a Corsair AIO cooler.
 
Should I spend the $169.00 and put this on it? https://www.evga.com/products/product.aspx?pn=400-HY-5598-B1

If you have ever used a blower card, that is what they sound like. On the other hand, it is a bit quieter than my  980Ti at the same fan speed. Personally I'd get the AIO and change out the default fans for a push/pull.  Silent gaming at 50C.

Do not buy the EVGA Hybrid kit at this time.  It is defective and EVGA is working on a revision.
https://forums.evga.com/1080Ti-FTW3-Upgraded-with-the-Hybrid-Kit-Problem-m2721450.aspx
 
Basically, it was breaking video cards.  Cards would be permanently damaged in such ways as stuck in low performance states, freezing, or artifacting.
 
Make sure that, if you buy a Hybrid kit, it is a new revised version.

ty_ger07
Do not buy the EVGA Hybrid kit at this time.  It is defective and EVGA is working on a revision.
https://forums.evga.com/1080Ti-FTW3-Upgraded-with-the-Hybrid-Kit-Problem-m2721450.aspx
 
Basically, it was breaking video cards.  Cards would be permanently damaged in such ways as stuck in low performance states, freezing, or artifacting.
 
Make sure that, if you buy a Hybrid kit, it is a new revised version.

Yeah that's going on for the ftw3 hybrid.. not heard of it for the regular 1080ti hybrid model.

Personally if I had a fe card I'd be going with a ek fe block. Hear way too many bad hybrid pump stories around here.

Microcenter even carries the ek founders edition block.. They also carry the hybrid block in the store as well.. so one could just return it if there was an issue with the pump.

AHowes
Yeah that's going on for the ftw3 hybrid.. not heard of it for the regular 1080ti hybrid model.

Personally if I had a fe card I'd be going with a ek fe block. Hear way too many bad hybrid pump stories around here.

I'm glad I got lucky...  
 
I snagged a 1080 Ti FE at release... then picked up the Hybrid kit at launch after a fast page reload and it's been flawless for the last 10 months or so.
 
Silent gaming around 43C... silent stress testing has peaked at 49C.  (Nice ambient temps in PNW year round)
 
Can't say enough about the hybrid kit.  The FE card was annoyingly loud with temps peaking around 80C as I recall. 

I have two 1080Ti FE and with a blower fan at 70% fan speed, which is needed to keep it cool, it sounds like a hairdryer on the lowest setting. It didn't bother me at first since I use headphones but you can still hear it during silent moments in games which ruins the immersion, oh and the card gets hot. I bought a full custom loop and I can now hear myself think whilst keeping the card cool enough to run the XOC BIOS.
 
To put it into perspective here's a few results on Unigine Superposition from my top card on +175/+700 with the blower fan. Can get more out of it with a water loop since it's not thermally throttling. The top result is using a water loop with XOC BIOS, the middle is a water loop with FE BIOS, the bottom is a blower fan at 100% with FE BIOS.
 

The waterloop gives me an extra 2 FPS average at 4K in this benchmark but more importantly, it's quiet. 
 
Disclaimer: The 7900X may or may not have contributed to a higher score since at 4K it's still GPU bound.