We would highly recommend Lucia/Maurizio's apartment, location is 2nd to none actually, Pantheon/Trevi/Spanish steps/Navona all <500 meters (we used Google map so can tell exact meters :)) plus Via del Corso high street shopping also 300m away. It's a quiet side street, lots of cafes/gelatos and great for families. Also taxi ranks within 200m so again very convenient.
The apartment itself is recently renovated, all new furniture and appliances, best part is it is top floor so very bright and airy.