iMac vs Mac Pro

I used to use Mac's all the time (from 1986 with the Mac Plus) and went to the dark side when OSX first came out. I have now switched back and use a Mac Book Pro for home. I love Mac's again and want to switch the work to Mac.
The question is:- Is the iMac fast enough or do I need the Mac Pro. I used Office (but migrating to iWork & iLife) Adobe CS3 (Photoshop, InDesign, Illustrator, Acrobat + PitStop), QuarkEXpress 7.3, FileMaker Adv 9, Aperture, Firefox etc... I spend most of the day using the computer and love speed.
Advise would be good. The iMac looks good spec and is cheap (compared to a equiverlent hi end PC) but does not have the expanderbility. I have dual big monitors and have heard that iMac only clones not a proper dual monotir.
Thanks
Julian

From what you say you are going to use your Mac for, the iMac should be more than enough. Get the 2.4Ghz one (or 2.8Ghz if you love speed) with default RAM and then pump it up to 4GB with RAM bought from elsewhere like newegg.

The iMac can extend the desktop upto a 24", that is 1920*1200 with it's single link DVI port. So unless you are looking into a 30", the iMac should be fine for dual monitors.

The iMac will handle all those programs with ease. Make sure you get 2Gb of RAM though.

I would max out the RAM

iMac is a great machine. I know on my iMac it only mirrors the screen.

@ Goobimama: They max at 24" which means a 4" monitor?

If what you do is alot of video editing and full dual monitors I would suggest the Mac Pro.