I've done it twice. In the Varieze I put together I had a Delcom mounted in the panel. Cool thing about the Delcom, Was that it uses mechanical controls and they are on the end of the unit, not the front so it only took up a few inches in the panel. I had it hard wired with external antenna and wired to headsets. It worked pretty well, long cross countries, etc.
Last year I had to send my only com into Garmin and I hooked my SP400 to the external ant and used a headset adapter. I tested it at various distances from local towered airport and the controllers gave me loud and clear responses on every test. I had only tested to about 35 miles out at 2.5K.
That said, another cheap option is an FL760 com. Installed it in my last plane, a Velocity, as a 2nd com. Worked better than the KX155.