Realistically, the Mars II is more of a collector's item than a legitimate solution. Granted it is a very impressive card, however its performance benefits do not warrant the $1500 Price tag. With that liquid cooled 590, you would likely be able to match the clock speeds of the Mars II without much trouble, and probably go even higher.
I really doubt you are doing anything that would require 2 590s
Its probably an over kill...Going with Man's golden rule of life, "No matter how big you are, its always nice to have a couple more inches"...LOL
I just figured having two would solve any future upgrades down the line...which could be 6 month to a year LOL...Now that I'm forced to think about it...Waiting and picking up another one cheaper in 6 months would be smarter...Thanks, Blade