Ps - to some degree there will be some bass roll off even wiring in before Bose amp ( cuts around 45hz approx from head unit) I am afraid the only way around this is either use a DSP or drastically change head unit !!) I opted to fit an Helix DSP and set up via their software supplied. Just depends how low you want your bass - 30 - 35hz this probably the options available - there are loads of discussions on the forums per the use of DSP,s and there is also a video review of the Helix DSP on YouTube
My DSP has been used to trim my rear door speakers , tweeters and sub and really opens up the possibilities of trimming to your own taste as well as the adjustability of the sound stage ( vital for centre stage when sitting in driver position - wifey doesn’t get a look or hear in haha
Cheers Phil UK