Hardware K20 or something else for computing (double prec.)

Hi all,

First post here, I hope this finds you well. I’m looking to get some recommendations. I’m just into this world, so I hope I don’t offend anyone my ignorance.

I’m looking to build a workstation for computing (in particular double precision scientific applications). What’s the best bang for your buck card in the price range: 900$-1500$, 1500$-2000$, and also > 2000$.

I’m hoping whatever I get could also do some rendering (but this is not the primary application, this would be more for interactive visualizations). It seems like the scientific computing cards are purely for number crunching. In that case, I think I would also need another GPU for the rendering. A nice recommendation here for a simple quadro card for rendering work would be welcome.

I’m looking for a bit of future proofness. I.e. if I get one of these cards now, I can just buy another one or two and plug them in my motherboard. Do I need and SLI connection for computing? (If I also end up with another GPU card for video I will need to make sure the motherboard has sufficient pcie slots)

It seems to me that the Tesla K40 is the top of the line workstation GPU (k80 is limited only to servers?).

Should I choose to build a workstation for our lab. Do I need to watch out for anything in particular to guarantee compatibility between parts. I.e. I think 32GB ram should be sufficient. And perhaps only a quad-core CPU is necessary… is a xeon chip recommended? Any computer cases to watch for too? Some of the cards look rather large.

Finally, can I purchase the passive cooled cards? or do I need the active ones for example: The K20x here is passive cooled:
http://www.compeve.com/gpu/nvidia-tesla-k20x-6gb-kepler-gpu-hp-c7s15a-712972-001-k20xm
Could I just use this or do I need an active cooled version?

Thanks again.