Is it worth keeping a GTX 660 to run second and third displays?

I've got a triple 1080 monitor setup and just picked up an MSI GTX 970 gaming 4G. My old card is an EVGA GTX 660 sc, and the machine is running an i7 4790k. I use the machine for gaming as well as coding and CAD for work.

Right now I set the 970 on my center monitor and the 660 for the other two. Will this make a difference in gaming performance versus just running all three off the 970?

Thanks!

Better off running all three on the 970.

The 660 is just going to cause higher power draw and also higher temps.

I am in the exact same boat (except I have two monitors), and it would appear from all of my research that the answer is going to be that having a 660 will be useful in games that are optimized for Physx. I would love to hear differently, but that seems to be the general consensus. Now, in your case, you have a third monitor; if you are running two DVIs and one HDMI, then I guess one card would do it, otherwise .... well I think you get it. So you have a two part question.

Physx Experiment

ATMINSIDE is absolutely right. It's not even worth it for Physix. If you absolutely need more than 1 card due to limited outputs in your 970, you're better off selling your 660 and putting that money towards a second 970.