After a longtime without anyway to crunch, back. I am once again contributing to SET I for evga. I'm also going to do milkyway as well. I am running my FX8350 at 75% until i get my custom water cooling parts I may need to drip it a little. I am only using a 760 right now. I would like to know if picking up a few cheap cards on the used market would be a good idea?

Welcome back.
There is a Setti challenge going on right now if you wanted to join in.
You have to sign up for it to be counted in. I am going to sigh in and help out some.
There is a thread for it with directions and links.
 
I use used parts, might as well save a few $$ and put the hardware to good use.
Prices are falling on video cards right now with the release of the new gtx10xx series cards.
I just picked up a gtx970 for 169$ B-stock.
Milkyway if I remember right uses DP and AMD cards like the R9-280x can be had for around 100$ or a little over.
I have seen GTX980Ti for 300$
 
There are good deals on used CPUs and motherboards out there as well.