For purely Linux use, IMO it was getting to be a no-brainer even on the Ivy Bridge (3rd generation) chips.

My work desktop came with a low-end business graphics card (Nvidia K600); I took it out and gave it back to the IT guys in favor of the motherboard video.

My laptop has Optimus; I need to build in enough Nvidia support to turn the chip off, and then I run just on Intel. I'd have to have a more complicated setup if I ever plugged the laptop into an external monitor some configurations of the external video ports require both video chips to be active, which is supported very poorly on Linux.

Depending on how big the python/php projects are and how much video editing you do, one of the better ultrabook-class i5 processors may be fine for your use.

For video viewing, Intel support on Linux is much better than either ATI or Nvidia.

For video editing, there's not much Linux support for GPU-accelerated encoding, and in my experience the quality at low bitrates of either NVidia's CUDA encoder or Intel's Quick Sync encoder are terrible to begin with. x264 is the gold standard AVC codec on Linux (whether you use Handbrake, FFMpeg, or something else as the front end, it's almost certainly actually using x264), and it really, really likes more cores. I don't know if you do enough of it to not just be patient with 2, but that's the one thing you mention that might make buying up to a quad core worth it.

I'd personally want 8gb for that kind of use; Firefox and Chrome can each balloon up to about a gig of working space.

Being a masochist, I run Gentoo on my work desktop, my home desktop, home server, and the dual-boot partition on my laptop. The VPS I rent runs CentOS 6 with no gui.