Choose HT and Music Rooms

Hi I have 2 Rooms in my house . One 19x20Ft on First Floor and another one 19x15Ft on Ground Floor. Wondering which one should i use for HT and 2 Ch Music. Any suggestions are appreicated.
One more thing. The room Upstais is a loft and i need to construct wall on one side to make it a room. So i am thinking of using the 15x19 room as HT room and use the upstairs room for music without making any changes to the room.
If you wanted to make a nice room for the 2 channel adjust the upper room with a wall and a storage area.
Make it the 'perfect' Golden ratio.(1.618034)
20 ft wall and a 12 ft wall box (adjust to exact proportions...)
Also upstairs would be better for 2 channel.. say if kids watching movie below way better thaan over your head if YOU are listening to music...
Agree! Music gets top tier. Eagles nest.
I cannot devide the upstairs room as this is next to the stair case and looks ugly if i devide it. How about using 15x19 room on Downstairs for Both Music and HT ?