One possibility may be the Backert Labs tube preamps. They have a unique “Green Force “ power supply and a pretty low 75 ohm output impedance. It’s made in the USA and they sell direct with a 14 day return policy. There are also about 6 dealers in the USA. My friend owns their Rhumba 1.3 and likes it quite a bit. It’s supposed to sound quite lively and have good PRAT (pace, rhythm and timing)
Although not a tube preamp I have an Ayre KX5 Twenty preamp and find it quite tube like in its midrange. It can also handle the DCS units 6V and it uses a unique volume control - the output voltage gain of the preamp is adjusted up or down with each click of the volume so the channel balance remains perfect even at low volume settings ( unlike Alps volume pots for example)