does it have a rail mount causey? If so, forget the M6, get a Streamlight TLR-2. more light, more battery life, less cost.
What do you want a laser for? the "oh cool" factor? or so u can hit your target? I saw a guy at precision once, couldnt hit the broadside of a barn without the laser. Hopefully, he never gets in a gunfight with dead batteries.