I just did this last weekend.

The oem bose snake wire harness in the trunk has full range left and right signals along with remote signal, power and ground.

I took the L/R and remote signals directly from it and power and ground from my trunk mounted battery and installed an amp with low-pass filter and two 10" subs! Sounds awesome! I still have two extra channels that I might use to install speakers in the rear like base and r1 have.

So, for those still with the oem Bose this is a great option if you want to stay relatively stock. I can disconnect everything and leave the Bose snake like nothing happened and keep the signal cables hidden!