mixing ohms?

hi i have a marantz sr53oo reciever which is 90 watts per channel [ 6.1 ] and it says on the back speaker impandance for 6 - 16 ohms speakers but i have

psb stratus bronze [ 4 ohms ]
psb c5i [ 4 ohms ]
yhamaha souronds [ 8 ohms ]
koss center suround [ 6 ohms ]

so my question is am i damaging any part of my system by mixing the impendance of the speakers and the reciever or did i buy the rong recevier for my bronzes

matt.

thanks in advance

I used to run a Marantz SR4200 into 4 ohm speakers even though it stated 6 ohm min impedance. I was told by my dealer "just be careful"! No problems there. As far as I know (and I'm happy for anyone here to correct me if I'm wrong) the lower impedance is just a higher risk of drawing too much current from your amp. But not cranking the volume should avoid that.