I believe I have finally decided on the Rythmik FV15HP for my subwoofer needs for now, although I anticipate adding another subwoofer in the future. In the end it came down to this one and the HSU VTF15H, in the head to head it went against the FV15 not the HP so I have a feeling the HP will edge the VTF15H out. And I like to have my speaker grills on and I am not fond of looking at two giant triangle ports on the HSU. Anyways, I see a list of options on Rythmik's page, and two of them interest me. First off, open for discussion is the two different amplifiers. The 600 and the 550, why do they offer two and is one more preferred over the other? And then I have to pay extra for spiked feet? This subwoofer will by sitting on carpet, do I want to spend extra for spiked feet or not?