Not a fan of Firefly.
For steak, try Via Brasil for picanha.
Nora's for Italian.
I know you said "off strip" but if you're looking for a romantic dinner for two - get an outside table at Mon Ami Gabi at Paris.
Surrounded by the neon lights of the strip, you'll have the Bellagio's dancing fountains as backdrop.
Every date I've been there with loved the cuisine and absolutely raved about the ambience.
Best comment, after we paused eating dinner to watch Bocellis' Con Te Petiro - "Thank you for giving me the kind of night most girls only dream about." (Chicks dig that water show for some reason, especially that song.)