Audio Research does not recommend that you use KT150s in their non SE amps. The modifications to SE are more than just tube replacement. The power supply (transformers) are upgraded to larger capacity transformers and other electrical changes are made to accommodate those new tubes.
I own REF 250 (non-SE) amps and contact Audio Research directly for their input on this and I was specifically told to not use KT150s.
You do so at your own risk. I would definitely not do it.
enjoy