What size of venues are you playing?
What will be going through the system?
How much experience do you have with PAs?
I work primarily in our PA department, and am admittedly something of a PA snob. But you REALLY need spend as much as you can. Cheaper PA gear sounds dreadful, and breaks down all the time.
Oh, and to contradict mikeluke, I don't know how new his Mackie gear is but their more recent stuff is dreadful. They still sound acceptable but they break down non-stop. I probably send five to ten 1501 bins back for repair every month, and they're service turnaround is laughable. Then there's the 350s and 450s...
The stuff they put out when they were still manufactured in Italy is great though, for the money, Find yourself a second hand Mackie set up that's more than 4 or 5 years old and you're laughing.
Stuff to look at now, in terms of lower priced PA, you can't beat KX Audio for bang for buck. Amazing gear for the prices.