Jim built the HTS sub to my specifications. Its genesis was my decision, well after purchasing a pair of HT1s and subject to my wife's lack of enthusiasm for a separate, large subwoofer, to add a high-quality woofer module that could also do double-duty as a home theater sub. In retrospect, if I had purchased an HT3 from the start, I would likely have gone with a single, 15" ported sub for HT effects. That said, I am very happy with this combination. The 12" driver has a ton of excursion and is in a very small box (1.3 cubic feet, if I remember correctly). I have a Crown K1 amp and a Behringer 2496 EQ to deal with the fairly high F3 of 50Hz. I think it's fair to say that this combination is the equal of the HT3 while offering the additional advantage of allowing bass management via the Behringer equalizer. It doesn't have quite the HT punch that you might find with a couple of 15" dedicated subs but it's plenty in my 22x20x9 room for all but the most extreme effects. To answer your specific question, there are separate binding posts for the HT1 and HTS sections. Design-wise, if I had to do it over from the start, I would have Jim install low-profile speaker cups and spikes to better couple the HT1s to the sub module. Right now, I use some super tack just to keep the kids or the dog from accidentally knocking the HT1s from their perch. If you your primary interest is 2-channel and don't have any tricky room modes to deal with, you should go with the HT3. If, on the other hand, you do have a problem room or have a big amp and want a little extra punch, the HT1/HTS combo may be the ticket. Good luck.
Mike