I'm hoping to get a Macbook Pro or Macbook Air, possibly a 4GB one due to budget restraints. I'm wondering though if this is enough? My current setup is a Windows laptop and I use Photoshop and Illustrator on a daily basis as I'm a graphic designer. Other software I use is Spotify, Microsoft Office (thought I'll probably switch to Mail once I have a Macbook), Skype and Chrome for browsing. If I decide to upgrade the RAM later on, is it possible to do this with a Macbook Pro or Air?