Hi there

At moment or foreseeable future I would suggest get Nvidia GPU(GTX1070 or 1070Ti is my suggestion) as you wouldn't be limited in any SW like Poser SuperFly or DAZ3D DS IRAY

AMD is supported in latest builds of Cycles and not sure if this build of Cycles will be implemented as should in future,if yes then this would be perfect but if you want to use yours GPU in other SW i would strongly suggest get Nvidia GPUs like GTX1070 or 1070Ti or earlier Titan X(these cards can be bought for £400)

I wish Poser would implement AMD ProRender which is awesome renderer I use this renderer in 3DS Max or Cinema4D and can be used with AMD GPUs without the single issue

Hope this helps

Thanks,Jura