GTX 650 worth the wait and extra money?

So I'm looking to get either 2 extra GT 640's or GTX 650's to power 5 extra monitors.

Now I'm wondering, should I go with the GT 640 or should I wait a week and go for the GTX 650?

The monitors won't be used for gaming or anything, just for the boring office stuff. I'm still keeping my GTX 670 for  the montors that are used for games and GPU intensive programs.

I would wait for the gtx 650. The gt 640 is a slow card because its memory on it.

If you're just using the extra monitors for office work, then just get the GT 640s, assuming that they will support that many monitors. There's no point in spending money on more performance when you're not going to need the extra performance anyway.