New Display Solution?

So I currently have a 19" Samsung LCD at home. I want to upgrade to a multi-display solution.

My thoughts were getting either a 22" or 24" wide screen and put my 19" as my secondary, or just getting another similar style 19" LCD and saving a lot of money.

I am not sure which setup would be more benneficial.

I use my computer (Mac Pro with x1950, so not worried about resolution). for:

Home Movie editing (Final Cut Express)
Picture editing (Photoshop and Aperture)
Matlab coding
SimuLink model building
C++ coding
And occasional gaming.

I do not watch DVD's or play any console games on my computer or computer display.

I use parallels to constantly swap between XP and OS X.

So what would be better/more ergonomic? 2 19"'s or 1 19" and 1 22" or 24" widescreen?