The pair of 4-10s are now in place, right next to the Double Impacts. They produce copious amounts of tight bass. My room is just over 22 ft. wide by 13.5 ft. deep with 9 ft. ceilings and I have the gain on each sub at about 15%. It took around 3 weeks to receive from the time of order. For some unknown reason (even though they were picked up at the same exact time by FedEx), one was delivered one afternoon and the other the next evening - I will never understand FedEx. We live kinda out-of-town a bit though. They essentially look like the DIs, but a bit shorter. I think I have them crossed over at around 55 Hz and the phase is at 0 degrees. I only have about 10 hours maybe of play time on them, but I think they are really nice sounding subs, especially for $800 each. To me, they fill in the gap between the DIs and my HSU VTF-15H subs in the corner. I was not planning on using the VTFs as well, but I am experimenting with setting the VTFs x-over way down near 35-37 Hz and bringing the gain slightly up from where I had it before the Tekton 4-10s were introduced into the system. And a reminder... this is only a 2-ch system - no home theater/surround.
