if ur still using that 1242 model then it will not matter because of the impedence ur sub will still be receiving only 200wrms
i once tried using both my subs in a well ported box powered off this amp with only 200wrms each & was able 2 shake objects about 100ft away with a nice clean bassline ....
I have been reading information all night and have learnt loads.
I'm going to connect one voice coil to channel 3 and the second coil to channel 4. I will run a dual rca cable from the back of the headunit (2 x subwoofer outs) to the amp which will make sure both coils are getting the same information.
This will mean the sub is still on 4 ohms getting 125w on each coil so 250w max.
I know it's only half the rated RMS but it's still better than nothing!
Tried installing the sub tonight. I first put the sub in series and linked that to ch3+4 bridged. It was VERY very quiet, I touched it to feel it vibrate but couldn't really hear anything from it.