Another Bose would be the easiest method, but not cheap. They do a cheaper 'compact' version that you could run off the output of your Tonematch mixer (do you have one?) and the necessary delays could be done from there. Failing that, any reasonable full-range powered speakers would do the job. Mackie, JBL and so on are good, with lots of cheaper options around. I use a DBX driverack to do delay stuff, and that works very well.
Tim