I just built a box based on the i7-4770S in an Asus H87M-Plus mATX board. The box uses the NOFAN CR-95C cpu cooler, which I found out during the build blocks the PCIe3 x16 slot.
I'm planning to run the Haswell graphics. I'm currently running a HD 5450 in an E6600 box and, other than Google Earth being doggie, I really don't notice GPU issues. (I'm not a gamer...)
But if HD 8400 lets me down and I want to go with a fanless GPU, I'm stuck with the PCIe 2.0 x16 slot. (Which Asus says runs 4x - compatible with PCIe x1 and x4 devices.) (???)
So what does this all mean? Can I install a decent video card (2560x1600) in my available slot and improve the graphics without starting from scratch? Will a x16 card work (only slower) in the x4 slot? Does a fast GPU require x16 bandwidth to twiddle bits in its on-board ram? Is PCI bandsidth the bottleneck, or is it GPU horsepower?