I use the Salamanders - WITHOUT sides and doors, and I still put my McIntosh MC2000 on top of a "bridge"-shelf as they call it, to let it breathe. What's wrong with showing off the tubes - esp. in the dark? :-)
C.J. has tube cages to hide them from animals and kids. I would not recommend to enclose the tube amp in any case since it will worm up the whole stand and the components arround it. To the amp itself it's beneficial to be hot and no ventilation the tube amp needs. As to your girlfriend you should probably make her face look sour or bitter on that particular issue :)
I own a salamander rack with mesh sides and the back pannel removed,it provides good ventilation for my BAT gear- which runs hot- and satisfies my wife. Incidentally, I have the frosted glass door which dresses the rack up a little and still allows all the romotes to work through it , higher spouse acceptance factor.