Watts is a unit of power output. For example, a speaker with a 100 watt amplifier will be alot louder than one with a 10 watt amplifier. My studio monitors are 75watts and i have never had any problems with them not being loud enough. Now if you are looking for good studio moniors,(im guessing you are talking about monitors because this is the home studio section)then you want a pair with the flattest frequency response you can afford, so your mixes translate better onto other systems. I have heard good things about the lower end Alesis, or even the Behringer Truths.
Moog