Yeah I know and the other advantage is a lot of monitors accept various inputs so if I got the Mini I could use it to watch tv or play a console on as well.Mini + monitor would typically cost more than an iMac, especially if you get an IPS panel, but you'll probably use the display years longer than the Mac, so the next Mac (or PC) will be that much cheaper since you don't need a display.
But if I can get a fast 27" iMac and it still lets me upgrade the RAM that might be too much to pass up.