I can’t figure out why the "SE" designation"Special Edition" Some better parts usually
The gain on the Aragon is 28db, which is normal (most amps are 26-30 db). The max gain on the BAT is 20db, but it also has 70 db of volume control range (using a shunted control, so there should not be an optimal volume range for the volume control). As such, even with the gain, you should still have more than 40db of volume control. As such, you should be fine.
Regarding the Freya S v. GFP-750, the GFP-750 was ever so slightly smoother in the midrange, but the Freya S imaged better. Both have no grain. Over time the passive mode on the Freya S (and the OG Saga I bought on closeout for my desktop system) have really grown on me.
O.K., this explains it. The VK-23SE preamp has a transformer-coupled output stage. Thus the "SE" designation. Normally, the output stage incorporated capacitors (not claiming to know the technical reasons). Apparently, the transformer-coupling is superior to caps. Whatever it's doing, my VK-33SE sounds like a dream (also transformer-coupled)!
My understanding is that capacitors are normally used in the output stage to prevent DC offset from potentially damaging speakers. The capacitor acts as a high pass filter. There are other ways of dealing with the potential DC offset. Like many things in audio there are disagreements as to the least audible way to deal with DC offset.