hey pro, your advice system for VrayRT is required

Guys,
it is my pleasure to be with the source of professionals.
nVIDIA lead us for many years to the best graphics solutions in games and in design.
many years ago I join to the highest graphics level when I have my 1st nVIDIA Geforce card,
I was working with the beast wildcat
today, I am going to built a render machine’s using GPU solution.
So, I am confused with many things,
the main reason for the machine is to enhance the speed of rendering without missing any part of quality.
I was decided to built a dual xeon E5 8 core cpu, and 8X GTX 680 VGA card,
I read many threats that said the older model 590 is stronger in cuda rendering!!!.
Also the Vray OpenCL is working in another way, it doesn’t use cuda for rendering, is that true?
many people suggest me for this type of rendering to have ATi 7970…
and others suggest to use less hardware so the budget can be less to, like i7-3930k, 32gb, 4X GTX590 or 4X GTX680
BTW, I am using 3dsmax for small graphics works and medium level of animation, like LOGO building, short animations stories, and so on.

I am looking for the best & fast solution, so the job can be done faster with less troubles.

waiting the pro suggestion

Mark

I’m sorry, am I in wrong place!!!?
correct me if so. :)