I knew of someone that put the NAV radio from a PT Cruiser into their Cirrus. Not only did they need to get the head unit and figure out the wiring to build a harness, but they had to grab the BCM from the PT and wire that into power as well - otherwise, as noted, the head unit wouldn't work.
Worth noting that the newer radios appear to be double-din in size, where the 95-07-ish vehicles used a 1.5 DIN size. In my recent searches there were no aftermarket sources for a 1.5 DIN head unit.