I don't understand why this is being sold as a Josh Homme signature amp. It was used on one of four bass tracks on Songs for the Deaf. All the guitars were other amps (Ampeg, TubeWorks, and an old PA-looking '70s Peavey). Did he use it on some later album?
I'm fairly certain those few bass tracks on SFTD aren't the only occasion where the Decade was used.
He does seem to layer big iron and small/cheap/unpopular amps like the Decade for tracking/overdubs, e.g. the Decade, but also a Gorilla, a cheap 90's Epiphone "starter" combo, and the small film projector amps that I mentioned, among others.
Some of the bigger irons he's using:
Tube Works RT-2100
various old Ampegs (VT-40, V4, V4B, VT-22)
Model T (V1)
Peavey VTM-60
a Bedrock combo
old WEM/Watkins stuff
Silvertone 1484
Peavey Standard 260
Peavey Standard PA head
The new Decade Too, from what I understand, is deemed "signature" because he helped with ideas for the redesign - additional high/low accentuation toggles and output options that make it more comfortable for studio use, and thus they put his name on it. After all, he's responsible for the stupid price hike during the last few years...
I can imagine he's laughing his ass off about the whole ordeal.