Ah, I had forgotten that they had done Reft. That makes five revisits (all of the Domain of Deneb, and the Solomani Rim) and three outside the Atlas bounds (Gvurrdon, Ziafrplians, and the other sector in Solomani space). Of those three only Gvurrdon had been officially visited before, and that only barely.
The "other sector in Solomani space" covered by Mongoose's alien modules is Alpha Crucis, which is in the Atlas but not otherwise previously detailed.
Surprised no-one has linked to http://dmckinne.winterwar.org/sector.html yet.
While we're talking about canonical or mostly-canonical data, the other sectors fully detailed by DGP should be mentioned: Vland in Vilani and Vargr, and Dark Nebula in Solomani and Aslan.