I'm just getting together my first pa, and I bought some notch filters, but they're only for my monitor speaker, do I need some on my main speakers as well? Currently I'm running a 250W X 2 amp, but soon I'll be upgrading to 500W X 2, does pa size affect notch filter application?

Hi , Firstly by Notch Fliters, do you mean Graphic Equalizers or actual Notch Fliters? Notch Fliter has a Higer Q (smaller Width)then a graphic Equalizer which is only 1/3 Octave,Notch Fliters are just to fix problems out of control, e.g Hum, Buzz, Feedback in a bad room, as for using it on FOH (front speakers) it is not usual @ all, If you are talking about Graphic Equalizers? you need them on both the Front Of House Speakers & The Foldback !!
One thing to remember with all Filters with a high Q !!
They always cause Phase Distortion & create Ripples @ Frequencies either side of the centre Frequency !!! so the least amount of use the better !!!
The better it will sound & the more Power you will be able to get out of your system

Powreamp !! the Bigger the better !!!
More Headroom is what you want !! so if you have a really Loud amplifier powering your speakers, you dont need to run your Mixer very hot @ all , so you have a cleaner Signal with lots of headroom !!

The requirement of a Filter are the same for very loud amps as no so loud ones, that is still all in the Line level domain( .775 Volts or 1.25volts Pro gear +8
Regards !!!!

Thanks that's a great answer, yes the notch is for feedback, I didn't realise that they were just for bad rooms, but that's a relief, I had terrible feedback in my living room.

Now I just need a gig.