Hi Binky --
There are two good online maps that I use:
La Netro and
Las Páginas Amarillas When you are on the home page of either of these sites, select "callejero". For La Netro, it is the option on the right hand side and for Páginas Amarillas it is one of the tabs across the top of the page.
While the two places that you have chosen are extremely close. You could walk from one to the other depending on how you are dressed. If I recall correctly, Kapital is near Atocha train station, around the corner from MadridMan's favorite "El Brillante".
Have fun!
Oh, with regard to the person who asked about teens... I think many disco's, including Kapital, have two different sessions, an early evening session for teens and then a late night session for adults. I am not a disco person of late (I was when I was here studying years ago), but I do know that there is a large disco on Gran Vía/Princess near La Plaza de España. I have seen tremendous lines of teens in front of it waiting to enter on occasion. Unfortunately I don't know the name of it. Maybe someone else can help out here.