HGS-15x uses same amp and driver as DD15

I recently got a HGS-15x with a Feb 06 build date. I am very impressed with the unit and inquired to tech support about the driver and amp. Apparently it used the same amp and driver as the DD15 without the SMS-1 type of room correction. Also, the box exterior is cheaper than the DD series to save money. So, if you are on a budget and really want the DD15, get a HGS-15x and SMS-1 and sonically you pretty close to the same thing. One thing that is missing is the variable feeback settings, so I am guessing the DD may play louder when allowed more distortion.
The HGS series are great subs, I'm currently running 2 HGS18's with an SMS-1 in a large room. For me it was a no-brainer, I got 2 used HGS-18's and a new SMS-1 for about the same price as 1 new DD-15. However, what I was told (also by a Velodyne service tech) was that the DD series utilizes a digital servo circuit vs an analog servo in the HGS series. For more information there is a dedicated Velodyne thread on the AVS forum. This question comes up quite a bit. I would also like to mention that Velodyne has the best customer service of any audio gear manufacture that I have ever dealt with. -Jeff