If your 19" runs at 1280x1024, then I think you can fit two of them side by side on a 30" monitor like the samsung 305t. It's native resolution is 2560x1600. I have a 24" an a 30" side by side, And if I have a window that is about 2/3 the width(1280) of the 24", I can drag it to the 30" and it occupies half the width. I think the key is that the pixel sizes are the same between the two.
And for what it is worth, I measure the horiontal dimension of the 24" at 22.3", and the 30" at 25.3".