I have the Mac Mini with the Fusion drive as well and I highly recommend it. If you're going to get an iMac you might as well get the 27" if you can afford it. I'm happy with the 21" monitor I have connected to my Mini. If I were deciding between an iMac with either the larger monitor or upgraded internals (Fusion drive, RAM, processor speed) I'd go with the smaller monitor and and better internals. If you can afford it get both!