help...permanent med. blonde to temp. light brown

My natural hair color is light brown. I usually color with L'Oreal Excellence Medium Ash Blonde. My hairstylist hates my current color (thinks it's too "orangey") and thinks I should color it darker, like a light brown. I don't want to do it permanently, so I want to try a semi-permanent, and I bought L'Oreal ColorSpa Light Ash Brown.

The instructions on the ColorSpa recommend against using it if you use permanent haircolor to lighten, so now I'm kind of apprehensive about using it, but I don't want to go permanent now. Why do they recommend against using it if you permanently lighten? What problems could happen if I used it anyway?

Next question: the directions recommend first-time application procedure if this is your first application of ColorSpa or if the ends of your hair are lighter than the rest of your hair (which are true for me. But they recommend touch-up application if you have used a permanent color (which is also true for me). So... which one should I use??? The directions contradict themselves!

Any answers would be appreciated... Thanks!