I have found DIY to be the best answer.
From the spouse's perspective, it is like a hobby because you are actually building what you listen to. It is more like a craft and thus it is something she can understand. Plus, it is easier on her to hear:
"This would cost $4,000 if I bought it commercially, but I built it for $400!"
Than: "Hey hon, I just spent $4,000 on this black box that makes sound!"
Even though you spend the same amount of money in the end anyway...you get better sound! And YOU built it!
The earlier mention of "its parts" for incoming boxes is a godsend. I have turned my basement into a mass of parts and bits for projects in-progress.