I am looking to purchase either 2 Polk 6x9 2 ohm subwoofers or 4 Onkyo 6x9 2 ohm subwoofers. The Polk subwoofers were originally part of the C-4 subwoofer enclosure Polk made in the 90s. The Onkyo 6x9s were sold by parts Express earlier this year but have since sold out.