+1:
We just started using a new system built around the Soundcraft Gigrac 600 and Peavey PR12Ns. They work together beautifully. For relatively cheap speakers the Peav's have impressive clarity, which you most likely want -- we were looking for something that just reinforced the sound volume without coloring the "acoustic" feel, and it can be done on a budget -- almost.
The PR12's are also quite lightweight and easy for Mrs Highlandman to tote around. The mixer is built like a tank. I recommend either the powered speaker or powered mixer route for a small system; a component system is just too much shtuff to mess with when transporting and setting up.
On the disappointing side, we put in a Kustom 10" wedge for a floor monitor. It absolutely sucks compared to the Peav's and will be replaced as soon as possible.
Some other tech points: you really don't need (or want) stereo for live sound, and yes, amp rating at twice the speaker rating is about right.
Garg is correct, building up a component system from scratch is a SOB, I've done it (sometimes well, sometimes not so well). A prepackaged system (powered speakers or powered mixer) gets you past some of these pitfalls. Beware the package deals at the discount houses, though, they tend to sell you speakers that are too large (in power handling) for the amps.
-Glenn