I am thinking of upgrading my centre speaker and would appreciate some advice. I currently have a Kef cresta, with Kef Q55's as fronts. My amplification is a Yamaha DSPE 800 with a Nad C340. I have noticed Kef 200c's are still available at selected locations and at a good price, however, I notice they are 4 ohm's, will this be a problem for my system and if so would I be better with a Q9? Please any suggestions welcome.