Thanks for all of the input folks. I've decided to go with the SLI 980ti setup. This has been a really interesting build. Everything was sourced via Craigslist and Black Friday/Cyber Monday.
Would have never guessed I'd end up going SLI...will be my first time.
I will be upgrading down the road (probably when we see a price dip on the new Titan, or when we get whatever succeeds the ti) I will be doing 4k gaming, but not until 4k/60fps is handled effectively by one card (hopefully for less than $1300 (with tax)