I've made it from Iceberg Lk to summit with a light overnight pack in 2 hours. Since you are day hiking, you might do it in less time. But it IS 2000' of elevation.
I've not made the Whitney - Muir - Whitney round trip, but 2+ hours seems reasonable. Seems like a 10-hour day to me, longer if you linger and enjoy the views.
You are likely partially acclimated if you live in Colorado at the typical 5k elevation. Most people in CA live near sea level, so the altitude difference is greater. When you come, don't spend a week at sea level first before heading to Whitney.
