I am running a Samsung Syncmaster 226BW on a Nvidia GForce 8500 and the 1680 x 1050 resolution seems needle sharp and trouble free.
The new monitor will surely behave using the old card i.e. unless it is really old and primitive.
I would risk it to have a top spec monitor and be prepared to buy a new graphics card later, though I don't think you will need it.
If you do much publishing, with the new monitor you will be able to run two applications or documents side by side and easily read both!