Yes, tube equipments got their own magic that make them very unique. ***
Fancy lightbulbs make great placebos, but besides that (and the high output impedance of tube amps) nothing special. Looking at them makes some men get all sappy, but that has nothing to do with their sonic properties.
Now, if you want a placebo, add a glorified lightbulb somewhere. It doesn't matter where. The only real point of it is for you to look at it and "hear" tube warmth.
Here's what I'd recommend.
Measure what's happening in the nearfield system. There will likely be some mix of rolled off highs/lows, and boosted midrange. (The SET amp may be relatively flat into a resistor, but not into a speaker with varying impedance.) Buy an
equalizer (such as a miniDSP unit) and copy the curve you find in nearfield system to the main system.