Second display options- I'm torn between two ...

Well, the main difference is the native resolution.

The 23-inch display, while physically smaller, has higher resolution (2048x1152). So you will be able to display more, but everything will be noticeably smaller.

The 24-inch display, has lower resolution (1920x1080). So if you want things to appear a bit larger on the screen (less eye strain), it may be the better choice. Fewer pixels spread over a larger area.

Those Dell displays use HDTV screen aspect ratio (16:9). This is +wider screen+ than Apple's displays. For example, Apple's 24-inch display resolution is 1920x1200 native. It has the same number of pixels left to right as the 24-inch Dell, but it has MORE pixels up and down.

So these Dell displays are not +as tall+ as typical +wide screen+ computer displays; they are better suited for use as HDTV screens. Vertical screen space is important for using a display with a computer, especially when you have things like the menu bar, Dock, and window title bar taking up part of that vertical space more or less permanently. I use an old-school 1600x1200 (4:3) non-wide display as my main display because I value the vertical space. Something to consider for either of these Dell displays.

ONE MORE THING: According to the specifications for you iMac

http://support.apple.com/kb/SP16

the max screen resolution for the external display is 1920x1200 (for a display connected over DVI). One of the "2048x1152" numbers for the 23-inch display exceeds the specs (although the other number being lower may make up for it). You should contact OWC to confirm it will work as a second display on an iMac.

1920x1080 should work. That's the same resolution as "1080i" for an HDTV and you can connect an HDTV as the second display. 2048x1152 is a less common resolution. In either case, it wouldn't hurt to ask the tech sales people at OWC; they know their stuff when it comes to Mac compatibility.

Good to know... Please post back when you get it to let us know how you like the display.

So you connect it with HDMI instead of DVI. That's interesting. That may be why the iMac could not figure out what the best resolution should be without a bit of help from you.

Glad you like it, and thanks for reporting back.

the monitor has both DVI-D and HDMI,
so dont make no difference what port you use,
i would have used the DVI-D,
less adapter

I realize they are the same as far as the video signal, but it may be some sensing thing done with the other pins. Doesn't really matter, as long as you are able to set it to 1920x1080 and it works.