You are doing well to consider alternatives while remodeling. Processors such as the Trinnov offer very good upmix features for two channel sources. The upmixer settings in the Trinnov can be tweeked to sound very similar to Trifield.
50 years ago (my early teenage years), I owned a Sansui Quadraphonic Receiver - followed by a Sansui Quadraphonic Integrated Amplifier - both feeding 4 x Celestion Ditton 15 Loudspeakers.
While I was able to play CD-4, SQ, UHJ, and QS encoded Albums via my Garrard 401/SME3009, I especially enjoyed the upmixng of conventional 2 channel music via ‘QS Synthesizer’.
Fast forward to the present day: I’m interested in your experience on what exactly is engaged on a Trinnov to facilitate similar upmixing of 2 channel music?