Would a GTX 660 be enough?

Hardware Hub GPU
1

Would a GTX 660 be Enough for 3 monitors, 2 1440x900 19" and a 27" 1920x1080

2

If you're not gaming, yes. If you're gaming maxed out, no. You probably could in less extensive games, but at more extensive ones, you may have to mix and match settings, or turn them all on low, or it wouldn't play at all

3

Id only be playing on the 27" monitor

4

Just for multitasking yes. And as Z said, gaming no. One monitor for gaming would work good.

5

Then yes

6

....ftfy.....