I have a Soundstream PN4.520D 4 channel amp and I am needing to know a good sub to match up with it. I am getting an under the dash sub box that holds one 8" sub. I am looking at either a Kicker 40CWS84 SVC 4ohm or a Powerbass XL-84 SVC 4ohm. From my research so far I have come to the...