Ok, im going to get things back on subject and offer a few opinions about the HDC3s
Personally, 3k on a copper coil HDC3 is ok, id just be careful, thats alot of power going through it. The alumnum coil is better suited for high power like that, but id still be careful with that much power.
Crownvic02 mention about babying subs, ......its not that dawg, you just have to be careful. Alot of times, your subs will let you know when they are being worked too hard, usually by smelling them or being extremely hot. I could get that 18 dust cap hot if I wanted too, but never came close to blowing the sub, because i was careful, and I beat on that bitch everyday.

Now with the tuning, you can tune a HDC3 low like 33 or 32hz and it will be fine. But, theirs a trade off. Your upper bass notes will suffer badly. My homeboy has a pair of the 10s off a AQ 3500D that was tuned to 33hz at first, but bumped it up to 38hz (he was using external areo ports, just cut them down to bump up the tuning) and his lows were still strong as ever, but his upper bass was much better and stronger.
For the HDC3s, I feel 35hz is perfect, DJ, the owner of AQ feels the same way.
Any sub playing below tuning is going to get warm, I know a guy online that plays his below tuning all the time, he adds low bass to tracks, so his subs drop all the time, tuned to 35hz. His AQs are fine.
I can vouch for those subs though, they got lows for days.
Ok, im done, and if anybody need a 18" I got mine for sale.