My setup is fairly simple, consisting of a few high quality parts besides my laptop.
I have a docking station for the laptop at my desk. This is connected to a Dell P2715Q 27“ 4k display, a Vortex Pok3r keyboard and a Logitech M570 trackball mouse. For audio I have an FX Audio DAC-X6 plugged in to te docking station and use Audio Technica ATH-M50x headphones.
As of January 2020 I also have connected to the external monitor a Raspberry Pi 4. I've found this little thing to be quite capable for most of what I do. I'm a little bummed that qutebrowser doesn't work quite right on it but Chromium runs just fine as do all of my terminal applications. I'm slowly trying to transition as much of my workflow over to this little setup. Sometimes I just don't want to pull my laptop out. Plus, it can do 4k at 60hz. My x220 can't.