I'll be shocked if you prefer the Deftechs.
This is a big sticking point for me as well. There is simply no way you're getting anything meaningful below about 30 hz or so out of that 8" driver. Probably less.
SVS publishes specs down to 28 hz for the towers and I've measured them. In my room they're actually pretty solid down to about 25 hz! Things drop off very quickly after that, but at east you can count on their published specs to be honest.
Yes, I love SVS and I'm being a shill... lol