went from 8GB down to 4GB and noticed the difference with Photoshop especially. I'll very soon be upgrading to 16GB, hopefully noticing a change in the opposite direction.

A lot of the so called speed isn't only down to how much ram you've got, but down to regular PC maintenance.

Regular disk optimisation, defrag and cleanup help remove and reorder unnecessary files and errors that really slow you computer down. Can save around 10GB of space if run once a month.