[G4] Graphics card upgrade to run 20" cinema?

[JayB]

Hi gang-

I tried finding this answer on the archives search, and via a general  
Google search- no joy.

I've got a AGP 500 upgraded to 1gig.  There's 2 RAGE 128 cards w/ 
2x16mb.  Running OS 10.3.9 w/ a gig of ram (this is my main Photoshop  
machine).

Just bought a 20" (cinema) Dell that has a native resolution of  
1680x1050.  I've held off as long as I can waiting for prices to fall  
on the LCD displays- my 17" CRT was way past it's useful life (won't  
calibrate anymore) and it's too small.

Just bought a 20" (cinema) Dell that has a native resolution of  
1680x1050
I don't have that option in my display options.

What do I need and are there recommended sources?  I hate to think  
the monitor is going to make me finally ditch this otherwise reliable  
old G4.

Thanks in advance for you help.

~Jay