I have several ATI Radeon X700 cards driving 28" monitors at 1920 x 1200 without any problems using the SDD version 3.1.8 build 505.
From what I have seen most of the PCIe ATI cards listed in the snap readme file will give that resolution and will also work with PCIe based motherboards.
Unless you have a requirement of something like HDMI output there is no need to discard the older cards.