Another option to look at my be the RSL Speedwoofer 10s. It's $400, but gets good reviews, and is small and more aesthetically pleasing then some subs. It has free shipping, a 30 day trial, and free return shipping if you don't like it.
None of these subs will fill your large space to reference levels down to 20Hz, but it doesn't sound like that's what your looking for anyways.
7.1.4 Theater Room (In Progress): JVC-RS46U, Silver Ticket AT 2.35:1 142”, Onkyo RZ830, Anthem PVA-7, Panasonic DBT-110, JBL Studio 270’s, 4 - 15" DIY Sealed Subs
3.1 Living Room: Samsung 64” F8500 Plasma, Anthem MRX 300, Dynaudio Audience 52’s, Dynaudio Audience 122C, NHT SubOne