Replace my B&W 802's?

I have an old pair of B&W 802 series 80's. These speakers were bought around 1987 and were produced before B&W made the matrix speakers.
I love the imaging and detail of these speakers but if there is one weak point, it's the bass. There just isn't much punch on the bottom end. Do I consider adding a subwoofer or is it time to move on from the B&W's? My budget for a subwoofer would be about $750-1000 for a used one. In addition, if the sub is not going to be worthwhile what are my B&W's worth and what kind of speakers might I consider?

Thanks!