I personally would go with one of the new mac minis. If you're getting by with your older imac and you're upgrading primarily for software needs, the mac mini is going to be just fine. Especially with the new update, its going to be substantially better. Aside from that, if design is your main concern, being able to choose your own monitor and monitor size is nice. Just a personal preference of course - but being able to choose a monitor that best suites your needs in terms of resolution and size is a nice option to have.