gogsard
it is a good brand. of course you cant find it at Brother's nor Cosplus.Try Brother Peter Damansara Uptown.
more info
http://www.epinions.com/MTX_Audio_10_____Subwoofer_Thunder4000_T4104__Subwoofers_Thunder4000_T4104/display_~full_specs
Anyway try the sub first before u buy it. Make sure the amp of yours can support your new Sub.