Front- and down-firing subwoofers -- Teufel Audio blog
Cerwin-Vega XLS-15S 15" Subwoofer - Additional 5% off at Checkout! – Sonido Live
Amazon.com: Klipsch Synergy Black Label Sub-100 10” Front-Firing Subwoofer & Synergy Black Label B-100 Bookshelf Speaker Pair, a 4” High-Output Woofer and a Dynamic .75” Tweeter, Black : Everything Else