I would say that it is conservative but after looking at the power draw of the 590's (almost 500W !!!) maybe not. Corsair has a good lineup for high-end PSU's you may want to check into. Either way, have fun bending space-time with that build
Pair of GTX590's - about 55 amps peaking to 60.
CPU - 10 amps.
That is something like 800 - 850 watts. Figure another 150 watts, max, for motherboard, RAM, and drives.
I would estimate power requirements at around 900 - 1000 watts. I'd put in a PSU of around 1200 watts. Unfortunately, I do not like the two that newegg sells. If you go up to 1250 watts, there are 4. I like either of the middle two: http://www.newegg.com/Product/ProductList.aspx?Submit=E...