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
I guess you could buy a 6 or 8 Ohm 25 watt (or higher) power resistor and put it in series with the positive speaker lead. It may degrade the sound quality slightly, but probably not much. Anyway, it would be a cheap fix.

Good Luck!
If just the center is the problem, you could buy an impedance matching transformer: Something like a 2 or 4 speaker selector that will make the speaker appear 8 ohms to the amp.
Thanks for the suggestions. Mark