As mentioned above ... quad core and modern integrated will manage fine. In lightroom you'll see slight delay to adjustments. i.e. you'll slide the adjuster, and it could be a half second pause/lag before you see the image adjust type thing. A seperate GPU will reduce that lag somewhat and make the whole thing feel more responsive. Opening and export RAW files is where CPU performance plays more. More cores/threads tends to result in more performance ( to a point ). Don't get me wrong though, quad core, its still very usable ... the difference will be in terms of a few seconds per image on open/export. For light use, that doesn't really matter.
Photoshop, I found it was a similar experience, I had a quad core 2400G AMD cpu running photoshop, and there was the slight lag to some operations and brushes. Usable, but slightly laggy sometimes. Adding a seperate GPU reduced that notably. Upgrading the cpu later again to 6 core improved performance also.
But I could still achieve all I needed to if i wanted with the 2400G.
16GB RAM will suffice as well.
