I had a Kenwood amp (old and weak) but it did the job using the PAC LOC and following the DIY.

That amp started dying so I upgraded to a JL Slash 250.1V2. I used the same LOC (but the JL did not have a +12v for external which PAC LOC needed). I left the power line for the PAC alone.

Now the bass is not as loud as it was on the Kenwood (which had an auxilary +12v for the LOC).

I'm thinking of using the direct RCA splice method, but won't the output be same as the LOC w/o power?

 

If you don't have the Bose system, don't use the RCA method without an LOC anyway. Otherwise, you will be feeding speaker level input signal into the amp.

Does the +12 volt source for the LOC have to be switched? If not, you can use the +12 volt power supply to the amp.