We recommend using powered speaker cabs - that is, speakers with the power amplifiers built in. With powered speakers, your system will survive if one speaker fails (any other solution means you lose all your amplification while it's fixed!). You will also need fewer bits of wire and it's much easier to set up. Modern powered speakers are also relatively light because amplifier designs don't need heavy the components that older designs use. You can also add more speakers with ease if you need more power without having to buy a complete new system.
A pair of powered cabs will cost about the same as a two channel power amplifier and passive (un-powered) cabs.