We just put in i7 computers where I work and they are AMAZING! I do graphic design and video digitizing, all in HD, so I can attest to the quality of the i7. As for graphics, I am running an ATI Radeon HD 5700 so you got me beat. Cooling and case, I have no input for you. I run and air cooled system so case and cooling are out of my knowledge. As for MOBO, I run an MSI 880GM-E41 and it overclocked just fine.
I will offer one piece of sound advice for you though. If you go Intel, get a Geforce video card, in turn, if you go AMD (which I did with an Athalon2 quad core) go with ATI/AMD products. AMD is also best compatible with MSI MOBO's.