Lots of love for SVS & others here...
I did a Dayton titanic 15 kit in my parent's great room. It is a very nice sub. Being sealed it will not go super low but has plenty of usable output to the mid 20's in 4,600 ft^3 to the point where it can still be obnoxious.
I have owned an SVS PB-12 Ultra 2 and the Dayton kit gives up very little in regards to anything but extension below the mid 20's.
I would not discredit this kit in any way without first hand use.