Hi
I am in the very same situation with more or less the same specs, and I see that to take photoscan to higher levels of accuraccy indeed you (and me) would need more processing power. However, I see in this forum that photoscan will eat whatever you throw at it with above than average work specs.
In my case, I will upgrade RAM but also operating systems and linux swap partition will run on a top notch SDD disk in case there is RAM memory pagination. Also a good CUDA card is very important, I have already one but will upgrade as soon as possible.