Is there anyway to add extra Amp and Sub to a 987 Bose for more bass?

[yfei]

On my 987 with bose I have to set the bass to -2 and tremble to -1. I am an audiophile The mid bass is too boomy, but at the same time it lacks of low end bass.
There seems no way to adjust this bose to close to neutral sounding, a little regret I should get the standard sound system. Maybe a good sub can add some low end bass, not a bad idea.