Imac late 2012 BOOTCAMP running slow for interior design use what should I upgrade?

Hi every one. I am running into trouble with my computer lately. I am using rhino 5 64bits, t-splines, panelling tools, GH and Keyshot for rendering. Until recently I was mainly doing furniture design, but I am now using this computer to design the showroom that my furniture manufacturer allocated me to display the collection I designed. It is painfully slow with all the above mentioned softwares. If I click once, I can go and make myself a coffee before it starts reacting. My design implies quite a few arrays of elements to create various patterns. My current configuration is an I mac late 2012 with 8gb 1600 mhz ddr3 of memory, cpu is a 3.2ghz Intel core i5 and the GPU is a nvidia GE force gtx 675M 1024MO. Can someone tell me where is the source of my problem between RAM, CPU and GPU and advise me on the configuration I should look for in order to sensibly improve the speed of my workflow? thanks for the help!

If your showroom model is significantly larger file size than your furniture models, I would say the prime suspect would be the 8gB of memory. Most people that are doing large models have a lot more memory than that; many have 32gB. Do you know anyone with a similar machine but more memory you can try it on?

Thanks for the tip. Anyway, it is seemingly the only option I have. Apple does not change the GPU on the Imac.