Not really.  I added a cheap $29 nVidia 8400GS PCI card to my aging P4 3Ghz setup a couple months ago and it runs my 22" and 17" monitors with ease in Ubuntu Jaunty (9.04).  I think if you stick with nVidia graphics cards it makes it a lot easier.  All I had to do was install the drivers and run the nVidia X Server Settings applet.