I believe that is what it was meant for as the HK system has a sub in the cargo area. The Subaru woofer comes with a T harness to hook it up to the OEM stereo.
Some useful info:
http://techinfo.subaru.com/proxy/63825/pdf/063825-H630SAJ000-ENandFRRevised.pdf
But you might want to check out my thread on an under-seat subwoofer installation I did. I went aftermarket for less than $200, which is less than the Subaru one. Although I haven't heard the Subaru version, mine has a bigger woofer (8" vs 6.5" I believe) and is fairly powerful at 120 watts RMS. This may be the ticket for what you're looking for. The Subaru one is probably more plug-n-play, but I think aftermarket should outperform it.
http://www.subaruoutback.org/forums...9-under-seat-subwoofer-installed-2012-ob.html
Some useful info:
http://techinfo.subaru.com/proxy/63825/pdf/063825-H630SAJ000-ENandFRRevised.pdf
But you might want to check out my thread on an under-seat subwoofer installation I did. I went aftermarket for less than $200, which is less than the Subaru one. Although I haven't heard the Subaru version, mine has a bigger woofer (8" vs 6.5" I believe) and is fairly powerful at 120 watts RMS. This may be the ticket for what you're looking for. The Subaru one is probably more plug-n-play, but I think aftermarket should outperform it.
http://www.subaruoutback.org/forums...9-under-seat-subwoofer-installed-2012-ob.html