Thanks for the advise guys.
I actually ordered everything already.
I stayed with the SSD for OS and apps and the raptors for storage, getting another SSD was quite expensive and it wasn't giving me a lot of space.
About the GPU I finally went for a 2GB NVIDIA GEFORCE GTX285. I'm actually using Maya for animation so, even if at some point I may need render power, I mainly live out of fast viewports so I think that'll do. Also, I understand that maya can only use one GPU, meaning that if you have 4 4870 on crossfire it will only use one of them, but I may be wrong.
About the quadro mod thing, I used it a long time ago and it didn't work out that well for me. It wasn't quite performing as a quadro on maya and it wasn't performing as a gaming card either. But maybe now that works better. I may try it and see how it works out. I just hope the GTX285 will do the job, and it was actually pretty good deal.
So the only thing left for me is wait and see how the computer performs and, who knows, maybe regret some of my decisions
Anyway, thanks a lot guys.