Assuming you have falloff turned off or are within it’s inside radius and have the spot lights ‘Use Inner’ turned off (Details tab) or have a non zero Inner Angle…
You have a number choices
1 – crank the intensity of the lights to over 100 (200 works)
2 – play with the material on the plane/floor/wall
-take the intensity of the Color channel of the material to over 100 (200 works)
-in the material’s Specular tab increase height/Falloff to 100 Width to whatever works for you.
-in the Illumination tab of the material experiment with Blinn or Oren-Nayar instead of just Phong they are more accurate(?) and will give different results in combination with Specular changes.