I have built stereo equipment sans chassis. In fact, most circuits start life without benefit of the outer enclosure, living on a naked circuit or proto board and they sound great. Once work has been completed on a circuit it's placed into a chassis so it can be used and sold as a package.
Chassis have a number of benefits: keeping circuitry shielded from noise, holding all the inputs and outputs in place, maintaining order in a cluttered space, managing heat and power. But chassis do more than functionally improve circuits. They help assign value to our equipment. Most of us judge the quality of what we purchase by its outer package: the quality of the input output connectors, casework, weight, fit and finish. Once we are past those indicators of net worth, we may peer inside to see what makes it tick, and lastly we listen to the complete package.
We don't pick unapealing mates, cars, art, or stereo equipment. If we can't feel comfortable with the outer wrap, it doesn't matter what's inside.
