If your on a budget check out the Solton Aart sat, it is the best system under £1000 I have heard. Has a nicely balanced frequency range with the all important mid range required for modern keyboards. It has an Active Sub and two Passive tops (via Speakon Connectors). The Amplification is via B&O ICE power. Honestly you will be amazed.

For the past three years I have been on a quest for a good quality system for our Audya customers- and apart from Ketrons own system the Solton blows everything else out of the water. Bose L1 system comes in a close third, simply because it lacks a little mid range.

For home use - Active Studio reference is the way to go, as Mirza says, the cost has come down massively and even budget systems are better than standard keyboard PA or those ghastly Yamaha MS speakers for Tyros.