I did a search for the harness you were looking for with no success of any info about it. I would not use a high-low converter on the bose system amps.

If you have rcas from the factory radio connecting to the bose amp, which I doubt, you can use a cheap pair of rca's lying around the house, or go to radioshack and buy the cheapest and shortest length and do a splice from the harness that you buy for you acura (metra 70-1720). use the outer-shield of the rca to the neg speaker lead from the radio, and the inner wire to the positive speaker lead from the radio on a single speaker. then repeat the process of the other three speakers to the amp.

if the signal going from the stock radio to the bose amp are normal speaker leads, then metra's 70-1721 harness should do the trick when adding the aftermarket radio with no modifications to the stock harness needed.