To answer your first question, yes, you will be able to run three monitors from either setup.
As to your second question, it's not going to make any difference at all really. Yes, technically the 7770 is faster according to this benchmark citing the exact scenario you're looking to compare.
Things to note:
-What is the total VRAM we're dealing with here in both scenarios? You're running three monitors, so I think the edge will most certainly go to whichever setup has the most VRAM. I know i use three monitors also, and it is way more taxing on the GPU then a single monitor, especially while gaming on one while it supports 1080p on the other two.
-Secondly, as you can see on the benchmark review, there is a VERY small advantage given to the 7770. No noticeable difference with those marginal improvements IMO.
-I think it may make a slight difference in fps (very slight) depending on which versions of the 7770 you have versus which model 250 you'd be buying. Either way, see the bottom line below.
BOTTOM LINE: If you already have the 7770 (like u say) then I'd stick with that. NO need to buy a 2nd card when the performance will be exactly the same as what you already have.
-hax0rmort
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