Firstly, as far as power rating goes, it depends whether you need to extract maximum power from your powered mixer or not. Lots of speakers are 8 Ohm, some are 4 Ohm and very few are 2 Ohm. The 2 Ohm rating is usually meant to cover the case when you wire speakers in parallel. Beware that speaker cables can be an Ohm or so, so you can lose a substantial fraction of your output power in the cables if you are not careful.

Secondly, the choice of speakers is heavily influenced by such things as:
(a) type of material you mainly want them to work with (folk, rock, disco, speech etc)
(b) the venue(s) where you operate
(c) preferences for physical characteristics: portability/ruggedness/size/weight
(d) preferences as to how they sound when driven by your mixer

It's not easy to get all these right. For example, some people like plastic cabinets as they can be lighter and more rugged than wood, but I happen not to like the sound they produce (as a generalization). If you can find some 150-200W 4 Ohm cabinets that meet your spec and that you like at a price you consider reasonable, go for them.

Boswell wrote: Firstly, as far as power rating goes, it depends whether you need to extract maximum power from your powered mixer or not. Lots of speakers are 8 Ohm, some are 4 Ohm and very few are 2 Ohm. The 2 Ohm rating is usually meant to cover the case when you wire speakers in parallel. Beware that speaker cables can be an Ohm or so, so you can lose a substantial fraction of your output power in the cables if you are not careful.

Secondly, the choice of speakers is heavily influenced by such things as:
(a) type of material you mainly want them to work with (folk, rock, disco, speech etc)
(b) the venue(s) where you operate
(c) preferences for physical characteristics: portability/ruggedness/size/weight
(d) preferences as to how they sound when driven by your mixer

It's not easy to get all these right. For example, some people like plastic cabinets as they can be lighter and more rugged than wood, but I happen not to like the sound they produce (as a generalization). If you can find some 150-200W 4 Ohm cabinets that meet your spec and that you like at a price you consider reasonable, go for them.

Thanks for the response. I see by browsing here that my question is very basic, so I appreciate you're responding.
They would be used for both my solo act, and for vocals for a band...not heavy, but rock with lead and 2-3 harmony vocals backing. Drums, bass etc. would not be put through the system. Venues would be small to medium sizes for solo, medium to large(churches etc) for band. Definitely want the vocals out front. Would want at least 12", I'm guessing, maybe 15". One speaker per side.
Thanks again.
Paulbob

Here is another rule of thumb. Power ratings on speakers generally indicate continuous power levels. Chances are, you will rarely run your speakers at their continuous rated power level. Regardless of rated power level, almost all speakers can accommodate peaks about four times higher than their rated power handling capabilities but only for peaks.

You can never have too much power. But you can have too little power. An underrated power amp, (that is an amplifier rated at a level you don't think you will need any more of) has a greater chance of blowing out your higher power rated speakers than a higher powered amplifier! How is that possible you ask? Simple. An underrated power amplifier will clip and go into heavy third harmonic distortion which produces incredible upper harmonics that heat up the voice coils in the speakers quickly until they blow out! Out of sight! Unbelievable but true.

For instance, I've always loved my Crown DC 300 type I I, which produces over 150 W per channel into my favorite old JBL4310/11/12's which are really only rated at handling 50 to 75 W. I've never blown them out but I monitor loud. Why haven't they blown out? Simple. They are highly efficient in that, an input of X watts puts out a level that is louder than an average speaker. Plus, the speakers can handle the extended peaks that the Crown can deliver without damage. I get loud clean sound without damage. So my amplifier is rated at least twice what the speakers can handle on a continuous level or RMS as opposed to peak.

But then I also recently purchased a pair of small KRK RP5's. I love them! They sound very much like my larger JBL's coming out of something the size of a shoe box! Pretty cool. I can mix on those things no problem and they were cheap! This is my second pair of KRK's. I like them because their sound resembles that of the JBL's closer than others and I happen to be a old JBL lover. All of those other crispier, crunchier sounding speakers make me want to vomit. I'd rather smash them with a sledgehammer. Keep those nasty crunchy things away from me.

Fat and smooth, just like me.
Ms. Remy Ann David