If you have 3000 watts for a pair of subs, I think the DD 3500's will be your best bet.
However, HDC3's are probably the best bang for the buck and will still do great off that amount of power.
Sleepy_jr's Envoy does pretty **** will with 2 18" HDC's in a box tuned for daily as TommyK will tell you. Of course he's coming out a little stronger this year //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif