Overclocked cards use exponential amounts of power. I once saw this explained in detail using a formula but after posting the link a few times, I haven't been able to find it. The K|ngp|n is I would say designed to run on LN2 and make headlines. We see very little improvement on 7xx / 9xx series.
Anything said by a paid representative of a company has be be taken in that context. MSI, Asus and Zotac don't seem to be having any problem keeping them in stock.
I have always poo poo'd the "just buy the cheapest one, they are all the same" advice. However, in recent generations, I am seeing little (if any) variation in actual performance between the Classified, K|ngP|n and actual fps. While looking at alternate BIOS, I do see peeps able to get higher core clocks, but when they post their benchies, they gained MHz but not fps.
EVGA advertises the K|ngp|n and charges by AISC quality
80% - $1,050
76% - $1,000
74% - $900
72% - $850
Same list is on the EVGA site
I just looked at my "plain jane" non reference Asus DCIIs and the AISC quality is 77% and 80%. I remember looking at my son's MSI Gaming cards and they were in high 70s.
And I agree wholeheartedly that we are getting less and less out of these cards with each generation, but I'd add even less with water cooling. I began to notice this with the 6xx series, with 7xx series it became smaller and with the 9xxs, unless you're building for noise or aesthetics, I don't think it's worth it. Right after I completed my custom loop Asus Formula / SLI build using the Asus DCIIs, I built another system with MSI MoBo / SLI on air. I got a higher stable OC on the air cooled build than I did w/ the custom loop.
PS ... Yet another thing that I find particularly annoying is that the card OCs are stable thru every benchmark you can throw at it. And yet some games just don't seem to like any OC. I don't play BF4 but my kids do and we basically had to set up a separate OC profiles for both CPU and GPUs. Now I noticed that Witcher 3 crashes after about 2-3 hours on my (Asus GPUs) box. My son has experienced the same thing (Twin MSI 970s) and took the OC off his cards. His housemate (Twin EVGA 980 Tis ) did the same.