Practical ways to deal with impedance/amp issues?

I'm piecing together a new HT system and hit a snag caused by some poor planning. Early on I bought a Revel Concerto sound bar. I thought it was going to be the front-end of an HT system while my tower speakers (Monitor Audio Silver 8's) were only going to be used for dedicated and separate 2 channel. The Revel is ok but for a complete front-end --- not so much. Now I want my Marantz 6009 to drive the sound bar as just the centre channel. If I use more than one of the speakers in the sound bar (there are 3 of course) then I run into impedance problems for the Marantz. Any ideas besides better planning? Thanks