If you are looking for a 20-22in Ultrasharp, I must highlight the
Dell 2209WA to you. It is a lovely monitor that uses an e-IPS screen, 1680x1050 resolution and 16:10 aspect ratio.
However, I would strongly suggest waiting for some indepth reviews of the
HP ZR24w. It is £75 more expensive than the 2209WA, however on paper it is much better. It is 24in, 16:10 1920x1200 (just like your 2407), uses an S-IPS panel (in many cases will be better than your 2407) and costs much less than other non-TN 24in displays. There should be an in-depth review of it in two weeks time on tftcentral.