I think the wire might be closer to 10 or maybe 12 gauge
The Monster cable that I used isn't marked.

I have tried another pair of 4 ohm speakers and they sounded bad also. The Polk's are new.

When I hooked up my Energy rc10's to it they sounded awesome. These are 8 ohm speakers that a borrowed from my bedroom. (I really like my RC10's)

Do you think the long cable run and the 4 ohm speakers are doing it??