I use Mackie HR824mk2 High Resolution Studio Monitor for center and surrounds. Retails for $850 each - I got mines new for around $550 each when Guitar Center was having a big sale. It sounds very good with my B&W 803D's for front mains. Eliminates need for multichannel amp, and has worked very well for me since I listen to 2 channel music about 90% of the time. I just could not justify spending multiple times more for center and surrounds that were timber matched to the mains.