Audio Systems: amp and speakers info, yamaha rx z9, consumer receivers

Question
Hi.I own an Yamaha RX-Z9 AV receiver with a minimum rms power at 8ohm =170watts x7 and 2x50watts for the effect channels. It also has a dynamic power rating for the main channels as follows. 8 Ohms=210watts, 6 ohms=260watts, 4 ohms=340watts, and 2 ohms=580watts. It only has two impedance settings: 6 and 8 ohms. I would like to know if I can use 4 ohms speakers for all 7 channels. I was looking at Polkaudio LSi series: LSi 15 for the fronts, LSi c for the center, LSi FX for the surrounds and LSi 9 for the surround backs. What do you think I should do? Thanks so much for your time.

Best wishes,

Anghel

Answer
I would prefer you use an 8 ohm speaker because most consumer receivers, even though they give 2 and 4 ohm ratings in their spec sheets, I know from experience that the current levels in the power output sections of these receivers is pushing their limits.  The long-term reliability is compromised with such low impendance - in my opinion.

However, that being said, if you like the 4 ohm Polks they should be okey if you watch the power level and don't overdrive the amps.  In other words if you are careful and attentive to the loudness levels you should be okey.

All the best,
Cleggsan