PC Build for iRender/Sketchup

I am new to this field but I have recently used the irender nxt trial with great results. I will be undertaking some new projects that will require lots of rendering of panoramic scenes. I want to get a new and more up to date PC that will help me render as efficiently as possible. 

My question is, what kind of specs should I be looking at? I know more as usually better, but what is more important: processor speed, RAM, or graphics card? In this case I am talking specifically for Sketchup and irender. I am also thinking that if I am going to get a new PC, I would also like to have it powerful enough to run Oculus Rift or other VR applications that seem to be imminent in the next year or so. 

Any suggestions? Thanks