Your ears, your room, your choice - as with all things audio, your ears should be the last word. Your environment isn't the same as anyone elses.
With ANY speakers, it's what you get used to. I would play several commercial CD's that you know, preferably in the same vein as your stuff, and adjust whatever controls you have for your tastes. Then, when you mix your own stuff, make it so you like it. Move it to different systems/rooms/cars, if you still like it your done...
Dunno, I just throw random, occasionally erudite sounding answers out every once in a while, sometimes it means something to somebody, other times screw 'em... :=)
Start with maximum setting - to have more control when equalizing highs.
If this sounds shrill with commercial CDs, or your mixes sounds dull on other systems, reduce tweeter level.