Does Studio Store Visualizer support multiple graphics cards and in what way will this increase the performance in Store Visualizer?
Store Visualizer works with multiple graphics cards on both Windows and Mac, as long as the multiple cards setup is supported by the graphics driver (SLI in the case of NVIDIA®, CrossFireX® for ATI/AMD®). However, the performance doesn't scale linearly with the number of cards.
Using two cards will not give you double performance but something more like 1.5 times, sometimes a little better, sometimes a little worse, depending on the situation. So, it is almost always better to get a single high end graphics card, rather than two lower spec ones.
In fact, there are two typical best-use scenarios for dual cards:
The customer wants even higher performance than what can be obtained with a top end card. In this case, you can use multiple top end cards (but not multiple lower end cards!).
The customer uses very high resolutions (e.g.: 4k). Multiple cards are very good at speeding up rendering if (and only if) the bottleneck is the resolution. In that specific case, one may double the performance when using two cards. But this implies that the performance bottleneck is indeed the high resolution, which is rarely the case below 4k.
Store Visualizer doesn't currently support multi-core CPUs when importing 3D models on Mac. However, this is not related to the rendering performance.