500w is chump change. It takes that to run 780's in sli, so in a single card? No biggie.
Those 2 cards are not for enthusiasts. They are for extremists. Enthusiasts are happy to have bragging rights with friends and neighbors... Owning even 1 of those cards would give someone bragging rites in States.
But I don't suffer from "little man syndrome", so if someone else wants one of those cards but can't justify the expense, or it won't fit in their favorite case, or they are just plain jealous because their precious 780ti just became 2nd class, does it bother me? Nope. If you can afford these cards, then go for it, and I'll be happy for you and I hope that they give you hours of enjoyment, because honestly, bitching about 3 slots or whining that its clc'd is absolutely pointless.