Rendering machine advice.

Hi folks.

I’m looking to put together a rendering machine, or at least that’s what I think I need to do. This would be for rendering stills and animations for Cycles and other engines. I really don’t like the idea of cloud rendering and want to control the process myself rather than farming it out. Yes I know all the arguments, and I know it’s going to be comparatively slow but this is the way I have to do things.

I don’t have unlimited cash and I’m getting confused as to the best way to build a powerful enough machine that won’t kill the bank of England. It’s worth mentioning this machine wouldn’t be the workstation.

I obviously need a good chunk of GPU memory, I’m currently using multiple GTX780’s which I think are 3gb, but I’m over running those. So the Q-M4000 looks like the starting point in terms on memory, but then I will need to get the Cuda count up with multiple cards and the M4000’s aren’t cheap. It is possible to use one M4000 for the memory and several smaller cards for the cores?

Then I get confused with the motherboard specs with differently rated pci-e slots, 16/8/4 etc. Do I need to be careful with this? There’s no point in putting a load of cards in a machine if they’re going to be throttled by a choke point. Or are the ratings only important for SLI situations?

Or, am I better off putting together an external gpu array?

I’m not new to modelling or pc’s, but I am new at trying to marry the two together! Any help would be very much appreciated.