Heheh, I doubt it. Electrons are affected by gravity, but I doubt it does much over the distances involved in tubes. Any differences in sound are almost assuredly due to differences in the circuits, not tube orientation.
Myself, I've been eyeing Super Bassman 800s these days. I dearly love my all-tube Super Bassman 300, but I seriously doubt that I'm ever running it hard enough to drive the power tubes enough to justify lugging them around. I'm always running it on the drive channel with the gain and the mix near dimed. The master might get a little above 3 if everyone else is running unusually loud, most of the time it's at 2.5 and I kind of wonder if I should turn down (and we're a pretty loud band). If someone else who shares our practice space uses it (Hehehe, don't even ask, you'll only bug me. It's so very unlikely you'll really abuse it more than I do.) and swtiches to the clean channel, they'll usually turn it up to 4 or so. When I show up afterward and switch it to the drive channel and forget to turn down the master before I hit a note, the rest of the band acts like they should report me for attempted murder.
So, a class D power amp with the same preamp as my current Super Bassman that weighs only 20 or so pounds sounds pretty appealing at the moment. Does anyone know a similar tube pre/class D power combo platter that might fit the same bill but instead runs less than around $900 used? Sticking individual components in a rack would be an acceptable solution, but I don't own a rack. So, think about that in your price calculations. Oh, and I want two inputs, because it does double duty as an organ or synth amp (yeah, I could buy a a/b pedal, but I don't wannnnnnnnnna). One channel with two inputs is fine, I drive them as much as I drive my bass sound.
If not, I'm probably gonna grab one.