What do I need to be able to run 3x 1440p monitors at once?

i would say the easiest thing would be to do productivity on 3 monitors, then the semi-gaming on the middle one when you game.
Especially if it's semi seriusly, already 1440p isn't semi-serius gaming, 3x1440p most hardcore gamers doesn't even game at that resolution.

Going for the single monitor would allow you to just buy one R9 290, it would run games in max detail on a 1440p monitor, and would just handle about medium settings when you want to show off or just want to play on all 3 monitors. Single card will allow 3 monitors since DVI-D also supports 1440p, and this card does have a DVI-D output. (the R9 280/280X also has DVI-D)

CrossFire as dual AMD gpu setups are named, will bring you much higher power consumption when gaming but in your case probably even more important, also when not gaming.

Would buy a single R9 290, then cancel the HERO board order and get a 4930K with a socket 2011 mobo. Since you're getting 4 DIMMs RAM and socket 1150 only supports dual-channel, it seems like your work if it's worth buying 32GB of ram for, would really benefit from the improvement of having quad-channel memory, which socket 2011 does come with, plus something that requires alot of RAM is usally also pretty CPU heavy, if you tasks are muti-threaded (check with specific applications) then the 4930K will really do you well, if not and the i7 4790K will be best. (coming to that below)

If you don't want to cancel it or maybe already recieved it, then it's fine too, since the socket 1150 is still very good, but, you do know that you can get a newer version of the i7? it's called Devils Canyon, the i7 4790K (i totally didn't just try to get you exited to buy this), it's like a good 4770K chip and it comes with a big clock improvement.


So buy the i7 4790K if you're not canceling the VII HERO, else buy the i7 4930K.
Get a R9 290 for gaming once in a while, which will bring beautifull scenery on a single 1440p, and will run all 3 screens over DP 1.2 and DVI-D. Dual gpu (aka. Crossfire) will take lump of extra wattage even when just doing productivity work, even when the pc is idle actually. Would avoid the cheaper Crossfire solutions here and only go Crossfire if you want to go all-in on all screens with two R9 290's.

Hope this helps somewhat!