I'm about 2 feet away (60cm) from a 30" display, and my home setup using a 27" iMac is about the same. So your desk would be plenty deep enough for me.
Are you keeping the keyboard on the desk? I find the iMac display a bit low for having the keyboard in front on the same surface -- works great with a keyboard tray though, which also pushes me back an extra foot from the desk, and makes the depth issue less critical.
As others state though, it all comes down to individual comfort. I think you'll have enough range to make it work...