The DGX-660 voice list shows that Equinox is voice number 140, and is selected by MSB 0, LSB 112, PC 95. The voice numbers are specific to a given model (if the model uses voice numbers, which some do not), but the MSB, LSB, and PC can be used to select the same voice on other models (if the voice is available on those models).
By the way, bank 0-112 is an XG voice bank, so it would be included among the XG or XGlite voices if a given model has it available.
The DGX-670 voice list doesn't show Equinox anywhere, and browsing through the synth voices in all categories-- including Legacy, XG, and GM-- reveals that voice 0-112-95 isn't included.
The DGX-670 doesn't have the ability to load voice expansions, so that potential solution is off the table.
Other than connecting to a computer or tablet and using a virtual instrument, or using a second keyboard that includes the Equinox voice, your best bet is to see if one of the other voices bears some resemblance to the Equinox voice and tweak its voice parameters as desired to get as good of a match as you can. You could try any of the other synth pad voices in the 0-112 bank, or PC 95 voices in the other banks, as those would presumably be nearest to the Equinox voice in general sound.