Most new monitors have both dvi and analog connections so it doesnt matter what your video card has. though it will be better quailty if you run both through dvi.
Look at the resolutions between the 20wide and 20standard. the 20standard 'matches' better with the 24. also the 20standard will be 'taller' than the 20wide so it will 'fit' better next to the 24.
heres a picture of my 24 next to my 20.
