i have 2.1 system grundig box 3600 and marantz pm 80 only. (100 watt speaker 100 watt amp) thinking suitable 1 or 2 12''subwoofers ( DIY OR BRANDED).but in budget .(max 20 k). can i make my stereo system more enjoyable ? low frequency range will improve my stereo listening quality . please suggest / guide. thanks to all.