I can't offer any advice for a gtx 750 ti, as I've never owned one.
In any case, you should be set if your card is even modestly young. Heck, I've had success with intel's crappy h55 (admittedly Intel has come a long way since the horrible integrated chipsets of old).
The most important thing I consider nowadays is triple-monitor support. Make sure the card can actually support 3 monitors, though - just because it has three ports doesn't mean it can run three monitors!
As for the setup, you're pretty much right, just go BIOS and select PEG (this is your card, it stands for PCI EXPRESS GRAPHICS). Remember to disable intel's card completely (in the bios) and plug your monitors to the right slot (again, your card, not your mobo). Then download the latest drivers and you should be set.
Considering the other system requirements, here are a few things to note:
- An SSD is very nice, especially to cut boot times, but if your main use is construct, I don't know if I'd bother. They're pretty expensive, and only make a difference with i/o heavy applications (such as photoshop, AfterEffects, AudaCity). If you're going to use the PC for gaming, SSDs cut loading times by a lot, but they don't do much else.
- If you're like me, you'll want to have a load of programs/tabs open at once, so you might want 8Gb of ram instead of 4Gb. Ram sticks are pretty cheap. If you have a choice, go with the biggest sticks you can grab (to give you room to upgrade), but get at least two sticks (so that you can dual-channel). I.e.: 2x4Gb is better than 1x8Gb as well as better than 4x2Gb.