Help Tannoy XT6F with Primaluna

Hello all. I have just purchased a pair of Tannoy XT6Fs that are supposed to replace pair of KEF LS50s. I am driving the new Tannoys with a PrimaLuna prologue premium power amplifier. It is the same amplifier I have been using on the KEFs. The Tannoys are almost unlistenable. The upper mid range is very peaky and there is not much bass. I have tried both the four and the eight ohm taps. I have also tried the stock EL34 tubes and some KT 150s. Both sound the same. I got out my old Rotel 990 solid state power amp. It sounds much much better on the Tannoys. I have read only spectacular reviews about this speaker. I'm running all Morrow cables. Any ideas? Thanks in advance.
Ben