Numa Tullo was a perfect place to stay, it's right on the edge of the lively evenings in Trastevere which you can go out and enjoy, but once you get back to your hotel, you can't hear any of it.
The only thing I will say is there is a huge variation in the size of the rooms, it felt a little ridiculous that we paid the same amount for three rooms but one was vastly bigger than the other two.