I think for a 6.6 gal that this would be overstocking. Neons in spite of being small need room to swim, and male dwarf gouramis can get up to 2.5 inches. They are also in general very peaceful but they are territorial and need some space in the tank to themselves. So it's possible your gourami might get frustrated and harass and stress the Neons to death.
They both recommended to need at least 10 gallons or larger. I would go with larger, 15-20 gals for 8 Neons and a Dwarf.
For a 6.6 I'd add a betta, a couple plants, a pretty Nerite snail, and a few shrimp.
As long as you keep the water in great condition you should be alright. It also just depends on the temperment of your fish. Sometime fish are really docile and don't mind smaller space, sometime they are more aggressive.
If your fish settle down good and don't harass each other and you keep up on water quality you should be alright. Does the tank have any decoration/hiding spots for the dwarf?
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