alpine type-r + pa500.4

elz88

Ok, i need some help! i have a one alpine type-r (swr-1242d) and a polk audio pa500.4, at first i had my cab running at 2 ohms with my amp bridged and i was wondering my my sub kept cutting out when i turned up the volume, i thought have might be a bad ground connection but after looking through the manuals the amp was pushing out 4 ohms which is bad right? so the only other option was to run my cab at 8 ohms with my amp running at 4 ohms bridged. it fine, but i not getting the full power out of my sub!!! is this bad? is there a way to match up my sub and my amp and the same ohms?