Unless Bryston upgrades the BP26 with its patented Salomie circuitry (and enables this upgrade to be applied to existing units), even if the PS3 is better than the MPS-2, substituting the former for the latter is, I suggest, highly unlikely to bring the performance of the BP26 up to that of the BP17 Cubed, let alone better it.
The BP26 is now a 17 year old design and, although it's been subject to a few evolutionary improvements over the years, it's well overdue for a wholesale revamp, perhaps to the extent of assigning the revised edition a new model number such as BP27 Cubed.