I am using Lowther EX3 in Voigt Pipes. I am running a 2 watt 45 amp. My room is 14'x24' with 16 foot vaulted ceiling. Also I have an open floorplan with little boundary area. I can fill the room quite well, and it sounds wonderful. However with this type of system, the bass response is limited to above 40Hz, and does not have the "slam" like many SS amp/multi-driver systems have. But is has many aspects that far exceed SS amp/multi-driver systems, too. It depends upon your needs. I rarely turn my system full-up. It is quite loud well before that. With a 15 watt Cary, you should be easily able to achieve 108db-109db peaks(at 1 meter) without compression, and still have 3db of dynamic headroom left in your amp.
Your amp will have enough power to push the DX3 to its maximum volume levels without compression, which is about 108-109db/1 meter very easily. You can go above that, but there will be compression of dynamics by the limitations of the single 8" drivers. If that is enough for you, then you will be satisfied, as long as the limited bottom end and lack of "slam" doesn't bother you. There is a little bit of "slam", but not what big power systems will give you. The clarity, detail, and coherence is worth it. IMO.
Your amp will have enough power to push the DX3 to its maximum volume levels without compression, which is about 108-109db/1 meter very easily. You can go above that, but there will be compression of dynamics by the limitations of the single 8" drivers. If that is enough for you, then you will be satisfied, as long as the limited bottom end and lack of "slam" doesn't bother you. There is a little bit of "slam", but not what big power systems will give you. The clarity, detail, and coherence is worth it. IMO.