If you like your keyboard, mouse and display, I'd go for the Mini.
Assuming you don't game.
You could always get the iMac and add your current keyboard, mouse and display to it.
I was in a similar boat, I was going to go for the 21.5'' iMac, but I wouldn't have been able to afford Apple upgrading the HDD, so when the Mac mini came out, I opted for the quad core mode, then I got 8GB of RAM, a 128GB SSD and 750GB 7200 RPM HDD. The thing flies. And my displays are an older 20'' Apple Cinema Display and a new 27'' thunderbolt display.
Couldn't have worked out better. Plus now, if I upgrade in two years, my displays are still useful for my next computer and I can sell the Mini to pay towards my new desktop if I'd want to
thanks well actually i play a few game occasionaly starcraft 2 and other and i want the machine to support at least high mode with light effect on ultra since i can do it with this computer (macbookpro 2010) but with 5 fps i believe that the new macmini with a dedicated video card can handle this on a 22 inch display anyway i won't buy an imac 27 because it is too big for me
i dont pretend to play on ultra but at least at the size of my display on a medium setting
did you payed 999 USD for the apple cinema is it realy that good?