I'd check out Torus PIU's,Bryston use to sell them under that name,now they call them Bryston BIT.
They are the same just different faceplates.
Huge transformers ect,since the newer Bryston sst2 have these new transformers and caps in their 7's,14's 28's there is no need for the PUI's.
I have a pair of 28's(older version)and use the Torus for those and it's a huge difference.
Also have the 7Bsst and 4Bsst with another Torus.
These I would never sell as I have compared to a few others and these really do give more stored power for the amps when required for dynamics in music.
I would think a pair of 7's would at normal levels use 14a,so a 20a Torus or BIT would suffice.