The Apple link doesn't show crap about supporting an external display
Support for external display in extended desktop mode:
Digital resolutions up to 1920 by 1200 pixels
Analog resolutions up to 2048 by 1536 pixels
Support for external display in video mirroring mode
Yeah easily. The card in your current imac will as well.
You'll get a single link of resolution which ends up being 1280 x 800 on the 30" panel.The Apple specs page says no. Well, you CAN use a 30 inch Cinema Display, but not with its native resolution.