Cass, I guarantee it will cover that size..I have already played to over 300 people..outdoors and the unit set up on the ground..

Ian , you are correct..two units will give you more separation, but keep in mind the K4 is a true stereo unit in a single unit..thus easily eliminates the chronic mono problem Yamaha provides..

Zuki mentioned a single unit, and the K4 is the best all around unit I have used...

It is surprisingly powerful, in fact it has been stated to be the most powerful keyboard amp to date[volume]..and it is feature lay-den..

I too love a big sound in stereo..and when I have the chance I still use my "old" Rolands separated about 10-12 feet..absolutely the best sound I have heard...but for the super best sound[especially vocals..the K4 [ by itself] or added to my Rolands[the latter, unbeatable]...maybe better than my Yorkville set up [2 NX520p's and a 600 Watt sub]..