Ages ago I was given some 3-500Z transmitting triodes and thought, wow, high-power SE amplifier. Then, after a bit of research, I realized the tubes were better off with hams, which is where they went. (I kept some smaller, pretty ones for my collection.) Here's the short version of why.
As you noted, the plate voltage is typically about 2 kiloVolts. Yes, 2,000 volts. (Pausing to let that sink in.) Two. Thousand. Volts. DC, not AC, but still enough to kill you just as dead as William Kemmler if you're not careful.
I have a pair of KLH Nines which need the power supplies rebuilt as the diodes are starting to fail. That's 5.7 kiloVolts DC, so it's not like I run away from HV power supplies. Just saying they're tricky to work on and I won't do it alone or without a home defib and my paramedic friend around just in case.
The critical issue, however, is not electrocution but the requirement for custom-wound output transformers. Given the voltage and power requirements those would be expensive for Class AB at 50 Watts, but if you want to run Class A the transformer must not saturate from DC in the primary, and this requires a substantial core, which greatly increases the cost, at least if one wants linearity. Guitar amplifier is a lot simpler.
A custom transformer, linear from 20 Hz to 20k Hz, matching 20k Ω to 16/8/4 Ω, and able to take 50 Watts is heavy and expensive. Maybe fifty pounds apiece, extrapolating from the 30 Watt Hammond SE (see below), figure a Cleveland per transformer since it's full custom and better specs. Plus the amplifier will exceed your floor loading.
Pete Millet built a 30 Watt amplifier using a PL-177 transmitting tube running at 625 VDC with a 5k SE transformer (Hammond 1628SEA at $150 apiece, quite a baragin). See:
http://www.pmillett.com/PL177.html