Huh, that Costco link doesn't work.
If all you're doing is music and zero HT, the VTF-2 would be a waste. Just get one or two of these JBLs currently on sale, with free return shipping:
www.jbl.com
You'd hear the biggest difference if you listen to a lot of bass-heavy music like rap, house, etc. and if your speaker has a high pass filter where you can have it do only the frequencies above say 80hz while the sub does everything under 80Hz ... THAT would make the biggest difference because you'd gain both headroom and clarity.
I doubt your speaker has that feature though...look in the owner's manual to check.
If all you're doing is music and zero HT, the VTF-2 would be a waste. Just get one or two of these JBLs currently on sale, with free return shipping:
SUB 550P | 500W, 10-inch powered subwoofer
What makes you feel the music in a professional venue is the same powerful force that will make you feel it at home: massive amounts of low-frequency bass. Through its light yet rigid PolyPlas™ cone frame, the Studio 550P subwoofer delivers powerful, nearly tangible deep notes and effects that...

You'd hear the biggest difference if you listen to a lot of bass-heavy music like rap, house, etc. and if your speaker has a high pass filter where you can have it do only the frequencies above say 80hz while the sub does everything under 80Hz ... THAT would make the biggest difference because you'd gain both headroom and clarity.
I doubt your speaker has that feature though...look in the owner's manual to check.