There are a number of tube preamps within your budget that have a lower output impedance. Jolida, Aric Audio, Quicksilver, Atma-Sphere, Van Alstine, Rogue, and others.
Otherwise look for an amp with higher input impedance. Either way when changing amplification, I would improve on the impedance ratio.
Giving your speakers are not attempting the lower octave you may not be hearing a problem with your current matchup.
Otherwise look for an amp with higher input impedance. Either way when changing amplification, I would improve on the impedance ratio.
Giving your speakers are not attempting the lower octave you may not be hearing a problem with your current matchup.