Please correct me if I am wrong:
Why should worry to get a 24" model for a "full HD" view, you do not edit the movie in a full screen mode. Final Cut has all other parts such as timeline, bin and effects window. The actual area you can see for the video is just a tiny box on the top-right corner. I believe dual-screen is a better option so go and get a 20" and a second screen for bigger editing area. Then get a usb or firewire output device to connect a full-hd display for full screen full quality rendering preview.
With the new introduced Final Cut Server you should not worry about the CPU speed too. just distrubute all your cpu intensive job to your other old computer or PC with XEON or Core2Quad which are all much cheaper to build.
I would get a 20" 2.8Ghz iMac and add as much RAM as possible and save the $$ for those I mentioned above
Typo?, the 20" is 2.66Ghz.
This is exactly what I ordered, with 4Gb Apple ram.
If I need to, I can use my old monitor for now, then if I want to upgrade the monitor, I'll go for a newer model. But I will not spend $1000 for it. There are some great monitors out there for much less than that, more like 3 or 4 hundred. Just my opinion.