Question for the OP ? Has the 240 been refurbished and or modified ? i run 87 db speakers with a heavily modified 240. Most 240 make 52-60 wpc before leaving the factory THD spec behind. Mike Samra does a great McShane style mod of the 240 if you are interested, A slug of Russian caps, much better power supply bits…IF you are running the tube cage, lose that.and try some HRS Nimbus couplers under the amp and your preamp. Re higher efficiency speakers, you have many many choices beyond Tekton, Go listen to a few before making the leap.
Jim