I would suggest you spend some time on the home page reading the A/V university tab, learn as much as possible on acoustics and what you can do or should do with your room. This is where most of the sound improvements come from, along with speakers.
Since you seem to be to involved with vinyl, not sure a sub would benefit you, unless those speakers you have just doesn't have much below 80Hz.
Most vinyls limits the bass intensity or your needle will depart