I know this is a silly comparison, but I thought I would post for anyone that may be interested in this comparison. I've only had the SVS for a day, but my initial impression is different than expected. Rather than sounding louder, the SVS actually seems quieter. I think because the Polk was much more "boomy." Rather than hearing the bass, I feel it more now. I haven't experienced that complete blown away factor yet, but I can tell you I have a serious headache after listening to the SVS for a couple of hours. Never experienced that with the Polk. I will take that as a sign that the SVS is creating a higher SPL.
I've been so used to associating bass with boomy noises, I just expected much more of the same. I almost don't even hear the SVS, just feel it. I hope this helps anyone interested in this comparison.