Bboring,
I 've had the Superfly and now the Superfly Supreme. I think your Rouge integrated amp will be fine using the 8 ohm tap. At 100 watts/ch the amp will be coasting. After you have had the Superfly and you think this is the combo for the longterm you can talk to Rouge about a 16 ohm tap if possible or just leave things alone and just enjoy.
They do make an 8 ohm 10" single driver for the Omen but I don't think it's the same quality of sound as the one in the Superfly. That's a question for Sean. In the Omen Definition and Definition the 2 10" drivers are wired together to produce 8 ohms. They can also be wired for 32 ohms on request, which someone with an OTL amp might want.
Hope this helps.