"it is not a good idea to base your decision on which preamp to buy solely on the basis of balanced outputs. First of all, they do not exist for tube equipment"
Perhaps some clarification regarding Balanced Tube Line-Preamps is in order...
I am currently running a Balanced Tube Line-Preamp (Audio Research Ref 6SE ) into a Balance SS Amp (Ayre V5). My understanding is BOTH boxes are fully-balanced (that is, they are not simply using XLR connectors, with single-ended circuitry). The cables are XLR terminated (High Fidelity Cables).
From the ARC marketing brochure: the 6SE is a fully-balanced, Class-A design with zero feedback."
If the hifi lore is true, the founding-fathers of both companies, William Zane Johnson (-2011) at Audio Research and Charlie Hanson (-2017) at Ayre strongly preferred designing balanced circuits for their equipment.
With that said, both boxes have single-ended connections as well to appeal to a broader marked. Why? Many sources are single-ended (ex. my Zest phono-pre is single ended output only, so the cable going into the ARC line-pre must be single ended).
Bottom line... Yes, you can buy a high-SQ Balanced Tube Line-Preamp that also has single-ended connections.
(my apologies if this was covered by prior replies, as I currently do not have enough time to read the full string)
Happy Hunting!