Thanks again for your responses.
In the end I opted for the "future-proof" option and the possibility of putting 64gb of RAM, which Photoscan gobbles up memory like crazy (I've seen configurations with 768gb of RAM to handle thousands of photos with said program).
With the i7 the CPU price went up by more than 60€, and it didn't compensate for the 37€ I saved with the DDR3 RAM. Besides, looking at Photoscan benchmarks, the CPU is not as important as the RAM and the graphics, so I save that money to build a future SLI of gtx 660, now that they are cheap.
As Espinete said, if I see that with the Skylake Refresh it's worth changing the CPU, I will, and if not.. long live the 6600k, as the change with the q6600 will be more than considerable.
I just have to thank you and apologize for the dizziness! I'll let you know how the new machine runs! 
See you soon!!!