I am switching from PC to Mac. I would like to use photoshop, aperture, and final cut express ( maybe pro in the future) I chose the 24 iMac with 2g RAM and upgraded video card. Will this machine be powerful enough for its intended use? Also should I upgrade to 500G Hardrive, or just purchase external HD as need arises? Is 2.33 GHz that much faster than 2.13? Thank you.