All 3 of them would certainly make a really nice gaming box.
But you have the wrong SSD / power supply in all of them. (they are great parts, but not the right great parts lol)
If you ever max out the two cards, they will draw in theory *but i've never seen in practice 1200w
Swap the 500GB evo for 2x 256 *the 500 isn't on the support list, it probably works perfectly, but from building experience you get a lot more support when things go wrong if you use what is supported, and with raid 1 disks your computer will be even faster than if it has a single 500. = better performance and better experience.
PSU your looking at a 1500w or 1300w at minimal (it is unlikely to EVER use that much but in the event it does, it won't blow, or cause major slowdowns/unexpected behaviour.)
I reckon it will use somewhere in the region of 650w flat out at ultra settings, but the efficiency will be good.
I used to think throw the best possible parts in, works great, but over the years i learned the hard way, thats not the way - the designers spend months testing parts - so only choose parts memory/cpu/ssd on the supported list.
I found you get the best performance and the most stable systems