I think 3-4 GB should be enough for product shots. Would that be the .obj file size for example?

Good to hear that the CPU and RAM are not a problem. I was under the impression that they could bottleneck the GPU.

The GTX 780ti and the GTX 970 seem to have minimum PSU requirements of 42A/600W and ...

460w (edited my first post).

I see the Titan Z is 1500 Euro, which is way out of my price range. I was thinking in the 300 euro ($400) price range. Will my existing CPU or RAM not limit the GPU then?

I'm unable to upgrade the PC for the time being. I'm not that tech-savvy to understand all of the requirements, so I'm hoping that someone could take a look and tell me which card is compatible?

I'm considering using Octane for product renders, but I don't know if my PC can take a powerful enough GPU. Is it possible with the following specs?

- Motherboard: GA-EP35-DS3R (rev. 2.1) http://www.gigabyte.com/products/product-page.aspx?pid=2743#ov

- CPU: Intel Q9550 http://ark.intel.com ...