Check out venues the size you expect to play, and see what the bands coming in there are using if they sound good. Ask about their PA when they take a break. Find out how much power they are running, how many channels they use, if any certain equipment has given them problems in the past, their favorite brand. Do a lot of research before making up your mind.
Here's a recommendation for starting out good but inexpensive:
Mixer -
http://www.billsmusiconline.com/yapmg166cx.html $399 ($30 cheaper than Musicians Friend
ttp://pro-audio.musiciansfriend.com/pro ... sku=630257)
EQ -
http://pro-audio.musiciansfriend.com/pr ... ku=180124V $99
Power amps -
http://pro-audio.musiciansfriend.com/pr ... sku=483052 $400
Mains -
http://pro-audio.musiciansfriend.com/pr ... sku=605100 $300 ea.
Monitors -
http://pro-audio.musiciansfriend.com/pr ... sku=600818 $120 ea.
Subs -
http://pro-audio.musiciansfriend.com/pr ... sku=606064 $360 ea.
Start out with 16 channel Yamaha mixer with built in effects $400
Tapco dual 31 band eq. $99
Tapco Power amp (750 watts for mains and 750 watts for monitors) $400
Two B52 dual 15 main cabs $600
Three Kustom 12 monitors $360
And there you have a good starting PA for less than $2000 not counting Mics, cables, mic stands etc.
Later add another power amp and the subs for $1120 and you've got a nice system that would handle almost any venue you would need to supply the PA for. (anything this won't handle will be big enough, they'd have a professional system)
Anyway, this was just a fun little search to get you headed in the right direction and show what you're looking at price wise. I'm sure many other BMixers will have comparable ideas with maybe better prices.
Yamaha is great gear with clean sound
Tapco is designed by Bob Mackie of Mackie Speakers
B52's are a good name brand
Kustom seems to be making a comeback by making good gear at low prices.
Any equipment I listed here that I haven't actually used, I read the reviews and they were all good.