Currently I run 3 21" Acer 1920x1080 in a 3 wide configuration. It was only after purchasing them (christmas sale at Newegg in 2012) I realized they didn't have vesa mounting hardware.

Not a problem at the time - they fit on my desk, so I made do.

I recently (~2 months ago) reactivated all of my accounts, upgraded them to WOD, and slowly came to the realization that my 2 x GTX 550Ti's just weren't going to cut it (or at least not cut it much longer). I purchased a GTX 970. Technology amazes me. A single card provides a 400% increase in performance over 2 cards in SLI purchased only about 2 years ago.

This card is (supposedly) capable of supporting 4 monitors (2xDVI, DP, Mini HDMI), of which I'm currently using 3.

I'd like to purchase a 4th monitor with more real estate than what I currently have (per monitor that is), with the intention of adding to it and replacing my existing monitors as I go along.

Save rainy day money for 4k? Find a 21:9? Introduce some portrait shenanigans to the mix?

I'd like your thoughts/opinions/recommendations on potential upgrade plans, ideally I'd like to generate a "roadmap" for the next year or so.

Thanks in advance aaaaaand go!