Don't want to interrupt Schmee's question and train of thought, but here's my two cents.
The iGPU will work with a dGPU PCI-E using Lucid Virtu. The performance gains and benches aren't too stellar, as I understand, but that's the setup I'm using. And I'm also using more power in "d-mode" with the monitors connected to the video card. Connecting your monitor(s) to the onboard iGPU and ports at the I/O plate is supposed to save you about 20W of power-usage with the dGPU socketed.
Depending on your pocket-book and over-clocking intentions, you might want to get a board that has the beefiest power-phase design. I can't vouch for the Gigabyte boards; the AsRock Extreme 4 seems to have many advocates here; my ASUS P8Z68-V-Pro has the same power-phase specs for a $200 mobo as their Maximus IV Extreme-Z $360 board.
But answering your original question while noting your focus in the successive posts following, I'd say stick with the Z68 chipset. And having no experience with Gigabyte Z68 boards, I can only say that Gigabyte has made some decent motherboards in the past, judging from my P45 "UD3R" board which I now use for a server system.