Upgrade from 2x 590 Classy to 1x 780 SC or 780 TI SC?

Thanks for the quick response, azathoth. For what it's worth, one of my 590's was given to me by a friend that was upgrading, so I'm not really factoring in (Oh well I spent $1000s of dollars for these cards!), I only purchased one of them. Also, I don't seem to be getting the performance I'd expect with the 590's whether the issue is driver related or otherwise; the 590's run hot (Mid 90's C while gaming, and I've seen it spike to 95+ recently, it was quite concerning) and they can get pretty loud with a custom fan profile to manage the heat they both put out. This isn't mentioning the random FPS dips and microstutter, or the lack of optimization for quad SLi. I should be home in around 4 hours, so I'll get some average FPS numbers for Ultra BF4 with my current setup - but it feels pretty low compared to the benchmark videos I've seen on YouTube and other benchmarks posted online for the 780 SC and 780 Ti SC.

EDIT: I just got home so I could test this, copy/pasted the message from work. On the map Zavod 311, my average FPS is around 70, ranging from 65-85, however this is with custom settings at 1080 resolution, every setting on high, and anti aliasing off. So, Custom, Everything on High with the last 3 options completely off. So that's with the 2x 590 classifieds. Then I find links such as this one: http://www.youtube.com/watch?v=dhlWeCY5aNk (at 1:55 he spawns into the Zavod 311 map I mentioned, and from the looks of it, gets better framerates with a single 780 SC. Keep in mind he has recording software dipping his FPS a bit, and his settings are also higher than mine, including AA being on.)

I don't want to be one of those guys that sees solid advice and ignores it, and I do appreciate yours greatly. I also completely agree that the price on the 700 series will drop in time, but we won't be seeing anything out of nVidia's 800 series for at LEAST 6 or so months, and even then, it won't likely be enough to drop prices on the 780/780 Ti. If I'd expect anything, it would be re-branding. I'd rather not OC my processor further personally, as I like it being where it is temperature/performance-wise, and based on my current temps for my GPUs, I'm not sure how much longer they'll last at 90 degrees Celsius and would like to get away from an SLi configuration for a while if I can.

Put simply, is the cost difference of the 780 SC and 780 TI SC justified in terms of performance to price ratio?

Again, thank you for you input Azathoth. It is appreciated, however I would like as many second opinions as possible before potentially dropping half a grand. As it stands, my 4 GPUs are running hot, and being outperformed by single GPU configurations. That tells me it's time to make a switch.There's also the fact that I would be gaining Shadowplay, which is easily worth a few bucks alone in my personal opinion.