You may be able to do a Star Alliance upgrade if you are on a Y or B fare ticket. It's segment-based (meaning IAD-NRT is one upgrade and NRT-TPE is another) and subject to the availability of business class award inventory. You cannot be booked on a codeshare, meaning your reservation has to have UA flight numbers.

As you'll be redeeming US miles, you'll have to request this through US Airways. They'll know the required mileage as well; it may be on the website.

I would have thought E+ would be complimentary too, but perhaps you're not on a Y/B fare and rather on a lower class fare that happens to be fully refundable. Of course, if that's the case, then no upgrade with US miles.