If you're looking for a classic tube sound suggest you try Quicksilver Mono's and leave the covers off if you want to see the tubes.
If you're looking for something interesting and different and can find it (used), David Berning made a stereo tube amp briefly for awhile that had a "see thru" front on it. I believe the model # may be the EA2101. I have not heard this amp but did try its ancestor, the EA2100. This was an unusual amp in that it the rich and transparent midrange of a tube amp but it had the bottom end impact and control of a solid state amp.
If you're looking for something interesting and different and can find it (used), David Berning made a stereo tube amp briefly for awhile that had a "see thru" front on it. I believe the model # may be the EA2101. I have not heard this amp but did try its ancestor, the EA2100. This was an unusual amp in that it the rich and transparent midrange of a tube amp but it had the bottom end impact and control of a solid state amp.