Bi-amping with tubes and SS can be tricky, matching different input sensitivities in the amps, etc.
You would seem to have plenty of power between the two Modwright KWA150SE's. The Modwright LS36.5 has a reputation for being a modern tube design, not sounding very tubey, or warm.
Perhaps you might consider trying a preamp that would give you that "seductive, slightly warm mid-range and top end that usually comes from tube amplification" that you seek.
Something along the lines of a Cary, CJ, Joule Electra, etc.
You could possibly get the same desired outcome with cables too. Look for something with gold in it as a conductor.
KCI Silkworm+, Jade, or Gabriel Gold may be just the ticket.
You would seem to have plenty of power between the two Modwright KWA150SE's. The Modwright LS36.5 has a reputation for being a modern tube design, not sounding very tubey, or warm.
Perhaps you might consider trying a preamp that would give you that "seductive, slightly warm mid-range and top end that usually comes from tube amplification" that you seek.
Something along the lines of a Cary, CJ, Joule Electra, etc.
You could possibly get the same desired outcome with cables too. Look for something with gold in it as a conductor.
KCI Silkworm+, Jade, or Gabriel Gold may be just the ticket.