I would go for the SVS because
Hey i did the same research like a month ago, finding out the best subwoofer for the price range of $500 to $700, and with all the responses from my fellow audioholics members and multiple reviews on other sites, I decided to go wit the SVS PB12-NSD Sub because:
A) It will be the the best bang for your buck (value for money)
B) the total price is like $769 and that includes shipping (affordabilty)
C) even though its big, it looks nice (Supereor looks)
D) great customer service from SVS (support staff)
E) It will last a long time (reliability)
F) very powerful and great quality (great engineering)
with all these factors and more, I did decide on the SVS PB12-NSD Sub, dont get me wrong the Rhythemic is a great sub, but when you compare it all around, I would not hesistate to buy the SVS, all the best