I want to set up 3 monitor with one 23in in the middle and two 22in on both side. I wonder how would the different in size affect the performance? Would it be too much different that I can't do eyefinity?
Assume they are all 1920x1080.
I would imagine that there would be no difference in performance because regardless of the monitor itself the video card is still rendering the images at a certain resolution and sending it out to the monitor to display. Whether the monitor displays it at the way you want it to (22" screen vs 23" screen) is up to the monitor. You would notice no framerate difference if that's what you're asking.
What you WILL notice is that the screens are smaller on either side. Personally that'd drive me crazy and I couldn't take it, but if you're OK with that then more power to you : )